Although no report is available on the role of intraovar-ian growth factors on follicular glucose metabolism for any species, EGF has been studied for its role in glucose metabolism in the liver and renal tubular cells. EGF stimulation of MDH activity for class 1 follicles may indicate a transient rise in mitochondrial glucose oxidation as observed in perfused rat liver preparation. EGF stimulates mitochondrial gluconeogenetic enzymes in rat hepatocytes and PFK mRNA expression in cultured rat fibroblasts via mitogen-activated protein kinase. IGF-I induction of PK and MDH activities in class 1 follicles, as well as PFK and PK activities in class 2 follicles, suggests that intraovarian growth modulators involving the tyrosine kinase signal transduction system may affect follicular glucose metabolism in a similar fashion. buy ventolin inhalers
Moreover, IGF-I may indeed augment glycolytic activity in multilayered preantral follicles, in which the existence of an oxygen gradient is likely. In cultured rat hepatocytes, IGF-I stimulates the formation of [14C]lactate from [14C]glucose up to 3-fold. IGF-I induction of enzyme activities strongly indicates that insulin present in the culture medium does not significantly affect follicular IGF-I receptor activity.
The results of the present studies provide the first evidence of TGFp modulation of follicular glucose metabolism, especially in human preantral follicles.