Francis Sunny

Rapid action of glucocorticoids on branchial ATPase activity in Oreochromis mossambicus: an in vivo and in vitro study.

The rapid action of cortisol and corticosterone on branchial Na(+)-K(+) ATPase, Ca(2+) ATPase activity and Na(+), K(+) and Ca(2+) ion contents was studied both in vivo and in vitro employing transcription inhibitor actinomycin D in Oreochromis mossambicus. Cortisol and corticosterone administration had significantly increased the activity of branchial Na(+)-K(+) ATPase and Ca(2+) ATPase in vivo after 30 min of injection, and the trend continued for 60 and 120 min for cortisol. The ionic contents were also significantly increased after 30 min in vivo. Na(+)-K(+) ATPase activity was significantly increased 5 min after hormone application in the in vitro system. Actinomycin D did not inhibit the effect of glucocorticoids on ATPase activity both in vivo and in vitro. It is concluded from the present study that cortisol and corticosterone produced a rapid stimulatory effect on branchial ATPase activity and ions in O. mossambicus both in vivo and in vitro. This effect could be due to a non-genomic action of these hormones since the enzyme activity was insensitive to actinomycin D.

Rapid action of cortisol and testosterone on lipogenic enzymes in a fresh water fish Oreochromis mossambicus: short-term in vivo and in vitro study

Rapid action of steroid hormones on lipid metabolism is not reported so far in any vertebrate. The present study was intended to evaluate the quick actions of cortisol and testosterone on enzymes, namely malic enzyme (ME), glucose-6-phosphate dehydrogenase (G6PDH), and isocitrate dehydrogenase (ICDH) in Oreochromis mossambicus. Cortisol and testosterone produced rapid and opposite effects on the lipogenic enzymes studied. Cortisol significantly decreased the activities of ME, G6PDH, as early as 5 min and ICDH as early as 10 min in vitro (10(-6) M), and 30 min in vivo (0.1 microg/g body wt.) whereas the same doses of testosterone significantly stimulated the activity of all enzymes as early as 5 min in vitro and 30 min in vivo. Actinomycin D treatment did not interfere with the inhibiting effect of cortisol on enzyme activities when measured at 10 min in the in vitro system. The transcriptional inhibitor appeared to partially block the effect of cortisol in vivo. The stimulatory effect of testosterone was insensitive to the action of actinomycin D both in vivo and in vitro. These effects appear to be brought about independently of new protein synthesis because the rapid responses occurred within a latent period of 5-30 min and were insensitive to the action of actinomycin D, suggesting a non-genomic action.

Sex steroids regulate intermediary metabolism in Oreochromis mossambicus.

The effect of long-term administration of testosterone, progesterone, and a synthetic estrogen, diethylstilbestrol (DES), on intermediary metabolism was studied in a freshwater fish Oreochromis mossambicus. The present study reveals that testosterone, progesterone, and Des specifically control key enzymes involved in carbohydrate, protein and lipid metabolism in the liver of O. mossambicus implying a general influence of sex steroids on intermediary metabolism. The activities of malic enzyme (ME), glucose-6-phosphate dehydrogenase (G6PDH), isocitrate dehydrogenase (ICDH), glucose 6 phosphatase (G-6-Pase), aspartate aminotransferase (AST), and alanine aminotransferase (ALT) are either stimulated or inhibited following the administration of sex steroids. The long-term in vivo i.p. injection of sex steroids intensely reveals that testosterone and progesterone are hyperglycemic, DES is hypoglycemic, testosterone and DES lipogenic, and progesterone antilipogenic (lipolytic) in the present study. It is also established that amino acid catabolism, mostly that of alanine, may be a major source of substrate for gluconeogenesis. A genomic mode of action is proposed for sex steroids for long term treatment, as their action is sensitive to transcription and translation inhibitors.

Genomic Effect of Glucocorticoids on Enzymes of Intermediary Metabolism in Oreochromis mossambicus

The present study examined the effect of long‐term treatment with cortisol and corticosterone on enzymes of intermediary metabolism, namely malic enzyme (ME), glucose‐6‐phosphate dehydrogenase (G6PDH), isocitrate dehydrogenase (ICDH), glucose 6 phosphatase (G‐6‐Pase), aspartate aminotransferase (AST), and alanine aminotransferase (ALT) in Oreochromis mossambicus. Cortisol and corticosterone regulate intermediary metabolism in the liver of O. mossambicus as evidenced by changes in the activity pattern of gluconeogenic and lipogenic enzymes and aminotransferases. The long‐term in vivo ip administration of glucocorticoids (GCs) suggests hyperglycemic, gluconeogenic, and antilipogenic roles of the hormones in O. mossambicus. The genomic mode of action of GCs is well established in the present study since the long‐term treatment is sensitive to the action of transcription and translation inhibitors.

Rapid action of testosterone and diethylstilbestrol on enzymes of osmoregulation in a freshwater fish Oreochromis mossambicus.

The rapid action of sex steroids on enzymes of osmoregulation has not been studied in teleosts. In vivo administration of 0.1 µg/g body wt. of testosterone and diethylstilbestrol (DES) significantly enhanced branchial Na+–K+ ATPase, Ca2+ ATPase, and Na+, K+, and Ca2+ ions as early as 30 minutes in a freshwater teleost Oreochromis mossambicus. Treatment with 10−6 M testosterone significantly stimulated Na+–K+ ATPase as early as 5 minutes in vitro. The same dose of DES also stimulated Na+–K+ ATPase activity within 10 minutes of incubation in a gill culture study. Administration of the transcriptional inhibitor, actinomycin D (0.1 µg/g body wt. in vivo and 10−6 M in vitro), prior to hormone treatment, did not prevent the steroid-induced ATPase activity both in vivo and in vitro. It seems that stimulation of Ca2+ ion may be responsible for the hormonal effects to increase enzyme activity. A possible nongenomic mode of action for testosterone and DES is suggested in Oreochromis.