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Dexamethasone induced changes in protein metabolism of silkworm larvae Bombyx mori (L).

INTRODUCTION

The information pertaining to the effect of vertebrate hormones on invertebrates in general and silkworm in particular is very scanty. A few investigators have made an attempt to investigate into the silkworm commercial characteristics (Thyagaraja et al., 1984, Bharathi et al., 1986, Karthikeyan et al., 1991. Bhaskar et al., 1983) reported that vertebrate pituitary extract influenced the growth, biochemical composition of silk gland and cocoon yield. There was an increased growth rate with shortened larval duration improved silk output and fecundity in B. mori when administer with prolactin. The psychological actions of the glucocorticoids (GCs) on intermediary metabolism include the regulation of energy metabolism. The actions appear to be mainly catabolic in effect, with an increased protein break down and nitrogen excretion. Recent years, the presence and activity of various vertebrate steroid hormones have been demonstrated in life system of insects (Goudar and Kaliwal,1999,2000). The effect of mammalian corticosteroids on insect growth, development and enhanced production has been extensively studied (Smith et al., 1968; Rosinski et al., 1978; Gawienowski et al., 1987). Belakeshan and Ray (1998) reported that a significant increased in silkland weight the treatment of estrodiol.

MATERIALS AND METHODS

The present work was carried out on "Swarnandhra" silkworm variety of Bombyx mori (L) belongs to the hybrid of [APM.sub.1] X [APS.sub.1] (Multivoltine x bivoltine) obtained from National Silkworm Seed Production Centre, NSSP, Central Silk Board, Ministry of Textiles, Govt. of India, Kadiri, Anantapur (Dist.) of A.P., India. Commercially available synthetic glucocorticoid, dexamethasone each tablet of 100 [micro]g was dissolved in 5ml of distilled water. The silkworms were divided into two groups, first group referred as control fed with normal mulberry leaf and the latter was treated as experimental and fed with dexamethasone sprayed mulberry leaves. The total protein content measured by the method of Lowry et al., (1951). The alamine amino transferase and aspartate amino transferase were estimated by the method of Reitman and Fraenkel (1957) as given by Bergmeyer (1965). The activity levels of Glutamate Dehydrogenase was estimated by the method of Nachlar et al., (1960).

RESULTS

The total protein, soluble protein and structural proteins were significantly elevated in intestine where as bodywall showed maximum elevation of structural proteins than the other tissues. The rate of increase was statistically significant in all the parameters of all the tissues over control respectively. The AIAT activity was significantly increased in all the tissues but the high levels of AIAT were observed in bodywall. The AAT activity showed no significant change in silk gland with drastic increase in both bodywall and intestine. The maximum increase was observed in bodywall than intestine over control respectively. The GDH activity also exhibited different trend like significant increase in bodywall and silkgland with non significant change in intestine over control.

DISCUSSION

The effect of dexamethasone in all the tissues of silkworm showed significant increase of total protein. This is mainly due to the inhibited proteolysis or the activated protein synthetic machinery. Since the silk gland forms the basic organ for cocoon formation and silk production (Krishnaswamy, 1978), probably the synthetic activities of the protein metabolism might have been accelerated through anabolic process by the hormonal treatment, (Bharathi et al., 1986). Hormones elevates the organic constituents, (Bharathi 1993) which supports present study. The effect of dexamethasone on silkgland showed significant elevated levels of soluble proteins also. This is mainly due to active protein synthesis under various stress conditions (Bhaskar et al., 1983, Bharathi et al., 1986;) and also due to inhibited proteolytic activity. Similarly, the effect of dexamethasone on silkgland also showed significant elevated levels of structural proteins and due to induced anabolic type of metabolism leading to increased protein content which reflects the higher silk production. However the rate of increase in structural protein content was lesser when compared to increase in soluble protein levels. All the above protein fraction elevations showed significant increased over control. Inconsistency, to the present results, several earlier investigators also reported the increase total protein content in silkgland, bodywall and intestine of silkworm larvae (Goudar and Kaliwal, 1999, 2000, 2001). Similarly, the soluble proteins and structural protein levels also increased in all the above tissues over control.

To understand the enzyme activities related to the protein metabolism, an attempt has been made to analyze the enzymes such as Alanine Amino Transferase (AIAT), Aspartate Amino Transferase (AAT) and Glutamate Dehydrogenase (GDH) in silkgland, bodywall and intestine of silkwarm larvae, treated with dexamethasone over control.

Since AIAT activity was elevated maximum in all the tissues on treatment with dexamethasone, anticipate the possibility of mobilization of alanine into carbohydrate synthesis, which might support the reported increase of carbohydrates in the tissues on treatment with dexamethasone. Several other investigators also reported elevated enzyme activities on treatment with estradiol, thyroxine, tenoxycarbe etc in silkworm larvae (Chaudhuri et al., 1996; Damodar Reddy et al., 1996; Skarlatos, 1996; Balakeshan and Ray, 1998, Goudar and Kaliwal, 2001) which supports the present study. The higher AAT activity showed that the diversion of aspirate amino acid towards tissue oxidations rather than efflux into haemolymph. Higher transaminase activities in the tissues indicates the increased protein synthesis as reported by Sinha et al., (1996). GDH activity was maximum in bodywall than silk gland suggesting the increased oxidation of glutamate, it shows that, oxidative deamination of amino acids can be envisaged. In consistent to the present study several investigators reported the elevatd dehydrogenase activities (Chaudhuri et al., 1996; Hemavathi et al., 2002) on hormonal treatment and also shows the elevated nitrogenous and products in silkworm larvae (Ramakrishna 2001), supports the present study. Finally, the results revealed that the protein metabolism was modulated on treatment with dexamethasone, whatever may be the mechanism of action, the results of protein fractions, proteins ratios and related enzyme activities provided clear evidence that the silkworm larvae, Bombyx mori responded to the influence of dexamethasone by altering protein metabolism.

REFERENCES

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(2.) Bharathi , D, Bhaskar M, Reddanna, P, Govindappa, S, 1986. Effect of vertebrate pituitary extract administration on organic content of silkworm larvae Bombyx mori. Ind. J. Comp. Animal. Physiol. 4: 9-12.

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(4.) Bhaskar, M., Bharathi, D., Reddenna, P, and Govindappa, S, 1983. Growth and biochemical composition of silkgland of Bombyx mori on exposure to pituitary extract. Proc. Natl. Sem. Res. Develop., 1,28-32.

(5.) Chaudhuri, A, Krishna, Ray, A.K, 199. Induction of subcellular malic dehydrogenase activity in fatbody cells of diapausing pupae of wild tasar Silkworm Antheraea mylita (D) 17-[beta] estradiol. Gen. Com. Endocrinol. 61: 82-86.

(6.) Damodar Reddy K, Chaudhuri, A., Thangavelu K. 1996. Influence of thyroxine on different Ion-dependent ATPase activities in fat body of Tasar Silkworm Antherea mylitta (D). Gen. Comp. Endocrinol. 104 (1): 20-28.

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(8.) Goudar, K.S and Kaliwal, B.B. 2000. Effect of Hydrocortisone on the economic parameters of the silkworm, Bombyx mori (L). Int. J. Indust. Entomol. 1: 35-40.

(9.) Goudar K.S, Kaliwal B.B, 2001. Effect of cortisone and Hydrocortisone on the biochemical changes in the fat body and haemolymph of the silkworm, Bombyx mori (L). Int. J. Indust. Entomol. 2(2): 181-184.

(10.) Hemavathi B, Thyagaraju K and Bharathi D, 2002: Effect of thyroxine on the activities of dehydrogenases in silkworm, Bombyx mori (L). Ind. J. Comp. Anim. Physiol. 20: 59-65.

(11.) Krishnaswami S. 1978. New Technology of silkworm rearing. Bull., CSR & TI, Mysore, India. 2.

(12.) Kurata K, Nakamura M, Okuda T, Hirano H, Shinbo H, 1994: Purification and characterization of a juvenile hormone binding protein from haemolymph of the silkworm, Bombyx mori. Comp. Biochem. Physiol. Ohwashi 1-2, Tsukub, Ibaraki 305, Japan. 109b (1)" : 105-114.

(13.) Lowry O.H, Rosebrough N.J, Farr A.L, Randall R.J, 1951. Protein measurement with the Folin phenol reagent. J. Biol. Chem. 193,265-275.

(14.) Nachlar M.M, Margulius S.P, Seligman A.M. 1960. A colorimetric method for estimation of succinate dehydrogenase activity. J. Biol. Chem. 235: 499-504.

(15.) Ramakrishna S, 2001. Hormonal regulation of growth and development in the larvae of silkworm Bombyx mori (L). M.Phil., dissertation submitted to Sri Venkateswara University, Tirupati, India.

(16.) Rosinski G, Piel L, Obuchowicz L, 1978: Effect of hydrocortisone on the growth and development of larvae Tenebric molitor. J. Insect. Physiol. 24: 97-99.

(17.) Reitman S, Fraenkel S, 1957. A colorimetric method for the determination of glutamic, oxaloacetic and glutamic pyruvic transaminases. Am.N.Clin.Pathol. 28 : 56-58.

(18.) Skarlatos G, Dedos, Hajime Fugo, 1996: Effects of fenoxycarb on the secretory activity of the prothoracic glands in the fifth instar of the silkworm, Bombyx mori. Gen. Com. Endocrinol. 104(2) : 213-224.

(19.) Smith P.D, Koenign P.B, Lucchesi J.C, 1968. Inhibition of development in Drosophila by Cortisone. Nature. 217:1286.

(20.) Sinha R.K, Srivastava P.P, Kar P.K, Thangavelu K, 1994. Lipid concentration in the pupal haemolymph of different races and F1S of six crosses of Antherae mylitta D. Geobios. 21 (3): 155-158.

Ramesh Babu Karumuru and Bhaskar Matcha

Department of Zoology, Sri Venkateswara University, Tirupati - 517 502, Andhra Pradesh, India.

E.Mail: matchabhaskar@yahoo.com
Table--1 : Consolidated table showing the levels of Total proteins,
Soluble Proteins, Structural Proteins, AIAT, AAT, and GDH in the
Silkgland of control of experimental V instar larvae. Values are
the mean of eight individual observations. Mean, [+ or -] SD., +
or--indicates the percent increase and decrease over control
respectively. "P" denotes the level of statistical significance.
N.S. indicates no significant change.

S.No Name of the Control Experimental % change
 parameter

1. Total Proteins 121.62 154.34 +26.90
 (mg/wet [+ or -] 6.62 [+ or -] 8.68 P <0.001
 weight of
 tissue

2. Soluble 37.23 49.25 +32.28
 Proteins [+ or -] 2.28 [+ or -] 4.62 P<0.001
 (mg/g wet
 weight of
 tissue

3. Structural 74.24 93.97 +25.76
 Proteins [+ or -] 2.28 [+ or -] 5.64 P <0.001
 (mg/g wet
 weight of
 tissue

4. AIAT 1.41 1.54 +9.21
 ([micro]) [+ or -] 0.12 [+ or -] 0.15 P <0.001
 moles of
 sodium
 pyruvate
 formed/mg
 protein/h)

5. AAT 1.15 1.21 +5.21
 ([micro]) [+ or -] 0.10 [+ or -] 0.14 NS
 moles of
 sodium
 pyruvate
 formed/mg
 protein/h)

6. GDH 0.790 0.840 +6.32
 ([micro]) [+ or -] 0.040 [+ or -] 0.060 P <0.001
 moles of
 formazan
 formed/mg
 protein/h)

Table--2: Consolidated table showing the levels of Total proteins,
Soluble Proteins, Structural Proteins, AIAT, AAT, and GDH in the
Bodywall of control of experimental V instar larvae. Values are the
mean of eight individual observations. Mean, [+ or -] SD., + or -
indicates the percent increase and decrease over control respectively.
"P" denotes the level of statistical significance. N.S. indicates no
significant change.

S.No. Name of the parameter Control Experimental % Change

1. Total Proteins 109.23 132.52 +21.32
 (mg/g wet weight of [+ or -] [+ or -] P<0.001
 tissue) 8.68 9.92

2. Soluble Proteins 42.56 58.23 +36.81
 (mg/g weight of [+ or -] [+ or -] P<0.001
 tissue) 3.91 4.24

3. Structural Proteins 54.55 73.52 +34.77
 (mg/g wet weight of [+ or -] [+ or -] P<0.001
 tissue) 3.42 5.78

4. AIAT ([mu] moles of 0.740 0.920 +24.32
 sodium pyruvate [+ or -] [+ or -] P<0.001
 formed/mg protein/h) 0.06 0.090

5. AAT (([mu] moles of 0.490 0.610 +24.48
 sodium pyruvate [+ or -] [+ or -] P<0.001
 formed/mg protein/h) 0.040 0.050

6. GDH (([mu] moles of 0.470 0.520 +10.63
 formazan formed/mg [+ or -] [+ or -] P<0.001
 protein/h) protein/h) 0.030 0.040

Table--3 : Consolidated table showing the levels of Total proteins,
Soluble Proteins, Structural Proteins, AIAT, AAT, and GDH in the
intestine of control of experimental V instar larvae. Values are the
mean of eight individual observations. Mean, [+ or -] SD., + or -
indicates the percent increase and decrease over control respectively.
"P" denotes the level of statistical significance. N.S. indicates no
significant change.

 Name of %
S.No. the parameter Control Experimental Change

1. Total Protein 82.42 96.07 +16.56
 (mg/g wet [+ or -] 5.10 [+ or -] 6.95 P<0.001
 weight of tissue)

2. Soluble Protein 42.12 59.34 +40.88
 (mg/g wet weight [+ or -] 4.17 [+ or -] 5.23 P<0.001
 of tissues)

3. Structural Protein 27.75 34.72 +25.12
 (mg/g wet weight [+ or -] 1.68 [+ or -] 2.81 P<0.001
 of tissues)

4. A/AT ([micro] moles 1.08 1.15 +6.48
 of sodium pyruvate [+ or -] 0.10 [+ or -] P<0.01
 formed/mg protien/
 h)

5. AAT (([micro] moles 0.670 0.780 +16.41
 pyruvate formed/mg 0.005 [+ or -] 0.080 P<0.01
 protein/h)

6. GDH ([micro] moles 1.08 1.12 +3.70
 of formazan [+ or -] 0.070 [+ or -] 0.090 NS
 Formed/mg protein/h)
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Author:Karumuru, Ramesh Babu; Matcha, Bhaskar
Publication:Bio Science Research Bulletin -Biological Sciences
Date:Jul 1, 2006
Words:2230
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