Alterations of ion-dependent ATPase activities in the brain of Singi fish, Heteropneustes fossilis (Bloch), by triiodothyronine.
The activities of Na+K(+)- and Mg(2+)-ATPases in mitochondrial, microsomal, and cytosolic fractions of Singi fish (Heteropneustes fossilis Bloch) brain were investigated after injections of various doses (0.012, 0.025, 0.05, and 0.10 micrograms/g) of triiodothyronine (T3) for 3 consecutive days. Both ATPases were found in the mitochondrial and microsomal fractions. The cytosolic fraction showed only Mg(2+)-ATPase activity. Mitochondrial Na+K(+)-ATPase activity increased to almost the same level in fish treated with 0.025, 0.05, or 0.10 micrograms of T3/g, while the T3 dose of 0.012 micrograms/g was ineffective in this respect. Microsomal Na+K(+)-ATPase activity increased to about the same level with all of the doses of T3 used. No detectable amount of Na+K(+)-ATPase was found in the brain cytosolic fraction. Mitochondrial Mg(2+)-ATPase activity was enhanced with 0.025, 0.05, and 0.10 micrograms of T3/g. The last dose, however, produced a higher increase in activity than the other two doses. Surprisingly, microsomal and cytosolic Mg(2+)-ATPase activity was not increased by T3 treatment. Although T3 concentrations rose sharply after each T3 injection, the serum T3 level in T3-injected fish was not different from that in the control as observed on the fourth day. The T3-induced rise of Na+K(+)- and Mg(2+)-ATPase activities was inhibited by cycloheximide treatment. Immersion of Singi fishes in thiourea significantly reduced brain Na+K(+)-ATPase activity in microsomal and mitochondrial fractions but decreased Mg(2+)-ATPase activity only in the mitochondrial fraction. Three consecutive daily injections of T3 (0.10 micrograms/g) into the thiourea-treated fishes increased their ATPase activities even beyond the control level.(ABSTRACT TRUNCATED AT 250 WORDS)
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Department of Animal Physiology, Bose Institute, Calcutta, India.
Dasmahapatra
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Medda
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D000818:Animals; D001921:Brain / Q000187:drug effects / Q000201:enzymology*; D017301:Ca(2+) Mg(2+)-ATPase / Q000378:metabolism*; D002397:Catfishes / Q000378:metabolism*; D003513:Cycloheximide / Q000494:pharmacology; D008861:Microsomes / Q000201:enzymology; D008928:Mitochondria / Q000201:enzymology; D000254:Sodium-Potassium-Exchanging ATPase / Q000378:metabolism*; D013890:Thiourea / Q000494:pharmacology; D014284:Triiodothyronine / Q000097:blood / Q000494:pharmacology*
D014284:Triiodothyronine; D003513:Cycloheximide; D017301:Ca(2+) Mg(2+)-ATPase; D000254:Sodium-Potassium-Exchanging ATPase; D013890:Thiourea