Effects of prolactin and growth hormone on tissue and serum carnitine in the rat.
Previous experimental observations have suggested to us that PRL and GH may be involved in regulating the metabolism of carnitine, a factor that plays a critically important role in fatty acid oxidation and ketogenesis. In the present study we administered bovine PRL (bPRL) or bovine GH (bGH) at a physiologic rate to hypophysectomized female rats for 2-3 days, and observed that bPRL caused a small (16%) increase (P less than 0.01), and bGH a 36% increase (P less than 0.01), in hepatic carnitine, bPRL decreased serum carnitine by 24% (P less than 0.05), and bPRL and bGH each increased the liver/serum carnitine ratio by 58% (P less than 0.01), suggesting that these hormones enhance the active uptake of carnitine from plasma. bPRL and bGH, alone or in combination, did not affect the carnitine content of cardiac or skeletal muscle, but in combination they increased the heart/serum and muscle/serum carnitine ratios by 45-76% (P less than 0.01), thus allowing maintenance of normal cardiac and skeletal muscle carnitine despite a decreased plasma level. In hypophysectomized male rats, bPRL did not affect liver or epididymal carnitine. We hypothesize that PRL and GH may play a role in the regulation of the carnitine concentration of female liver by enhancing hepatic uptake of carnitine from plasma, and through this mechanism may affect hepatic fatty acid oxidation and ketogenesis. The effect of lactogenic and somatogenic hormones on hepatic carnitine and ketogenesis could be of particular physiological importance in late pregnancy and during lactation.
Department of Medicine, Albany Medical College, New York 12208.
A D
AD
Goodman
S
S
Hoekstra
R S
RS
Busch
G S
GS
Meyer
S S
SS
Abend
D000818:Animals; D002331:Carnitine / Q000097:blood / Q000378:metabolism*; D004822:Epididymis / Q000187:drug effects / Q000378:metabolism*; D005260:Female; D013006:Growth Hormone / Q000494:pharmacology*; D006321:Heart / Q000187:drug effects; D007016:Hypophysectomy; D008099:Liver / Q000187:drug effects / Q000378:metabolism*; D008297:Male; D009132:Muscles / Q000187:drug effects / Q000378:metabolism*; D009206:Myocardium / Q000378:metabolism*; D009928:Organ Specificity; D011388:Prolactin / Q000494:pharmacology*; D051381:Rats; D011919:Rats, Inbred Strains; D012016:Reference Values
D011388:Prolactin; D013006:Growth Hormone; D002331:Carnitine