THE EFFECTS OF OESTROGEN AND GONADOTROPHINS ON LIPID AND PROTEIN METABOLISM IN XENOPUS LAEVIS DAUDIN

Abstract

SUMMARY The effect of exogenous oestrogen and follicle-stimulating hormone (FSH) on the concentration of serum lipids and protein has been investigated in the South African clawed toad, Xenopus laevis Daudin. Oestradiol-17β was implanted i.p. in mature females; the rate of absorption was 13·6 μg./day. Within 10 days the plasma concentration of all lipid components increased significantly (unesterified and esterified fatty acids, cholesterol, phospholipids). The lipid concentration tended to level out after treatment for 20 days. In contrast, oestradiol caused a steady and continued rise in the plasma protein level for up to 70 days after implantation. Electrophoresis showed that the increased protein concentration was due to the emergence of a new plasma protein or proteins with a high phosphorus, calcium and lipid content. Injections of oestradiol benzoate showed the responses to be dose-dependent; the lowest effective dose was 1·0 μg./100 g. body weight/day. Implants of oestradiol in males and hypophysectomized females resulted in a similar elevation of protein and lipid components. Mammalian FSH depressed the plasma lipid content in both untreated and oestradiol-implanted females but had no effect on the newly emergent proteins and their associated components. The results are discussed in relation to the effects of oestradiol on plasma constituents in other oviparous vertebrate groups.