Effects of steroid hormones on total brain Na(+)-k+ ATPase activity in Oreochromis mossambicus.
The effects of administration of cortisol, corticosterone, testosterone, progesterone and a synthetic estrogen. diethylstilbestrol (DES) on total brain Na(+)-K+- ATPase were investigated in tilapia, O. mossambicus. Exogenous administration of 0.125 and 0.25 microg/g body weight of glucocorticoids and 0.125, 0.25 and 0.5 microg/g body weight of DES for 5 days significantly stimulated Na+(-) K+ ATPase activity by 14-41% in the brain, while 0.5 microg/g body weight of glucocorticoids did not evoke any response on the activity of the enzyme. Progesterone (0.125 and 0.25 microg/g body weight) administration significantly decreased the enzyme activity by 21-36% and high dose (0.5 microg/g body weight) was ineffective. Testosterone exhibited a biphasic effect on Na(+)-K+ ATPase activity--a low dose stimulated by 14% while middle and high doses inhibited it by 19-24%. The results seem to be the first report on the effect of steroids on brain ATPase activity in a teleost. When 0.25microg/g body weight of actinomycin D or puromycin was administered prior to the treatment of similar doses of hormones, the inhibitors significantly inhibited the effect of the hormones by 24-52%. This clearly shows that the effect of the hormones was sensitive to the action of inhibitors suggesting a possible genomic mode of action under long-term treatment. The results suggest that cortisol, corticosterone and DES may possibly stimulate the co-transport of glucose and excitation of membrane potential while progesterone and testosterone inhibit them in the brain of O. mossambicus by regulating the activity of Na(+)-K+ ATPase.
Sunny
Francis
F
Department of Zoology, University College, Trivandrum 695 034, India. fsnature@sancharnet.in
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V Oommen
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D000818:Animals; D001835:Body Weight; D001921:Brain / Q000187:drug effects* / Q000201:enzymology* / Q000473:pathology; D003345:Corticosterone / Q000494:pharmacology; D003609:Dactinomycin / Q000494:pharmacology; D004054:Diethylstilbestrol / Q000494:pharmacology; D004305:Dose-Response Relationship, Drug; D005399:Fishes; D006854:Hydrocortisone / Q000494:pharmacology; D011374:Progesterone / Q000494:pharmacology; D011691:Puromycin / Q000494:pharmacology; D000254:Sodium-Potassium-Exchanging ATPase / Q000378:metabolism*; D013256:Steroids / Q000494:pharmacology*; D013739:Testosterone / Q000494:pharmacology; D017210:Tilapia
D013256:Steroids; D003609:Dactinomycin; D013739:Testosterone; D011691:Puromycin; D011374:Progesterone; D004054:Diethylstilbestrol; D000254:Sodium-Potassium-Exchanging ATPase; D003345:Corticosterone; D006854:Hydrocortisone