HEXOKINASE ISOENZYMES IN THE RAT PLACENTA

The phosphorylation of glucose to glucose-6-phosphate, the first enzym atic step for glucose utilization is catalysed by a family of four hex okinase isoenzymes(HKI-IV) which display a tissue-specific distributio n. The expression of HK isoenzymes was investigated in the rat placent a. High levels of HI;I and HI;II mRNA were found in the junctional and the labyrinthine zones. HKIII mRNA was present at low levels in the j unctional zone and glucokinase (HKIV) mRNA was not detected, indicatin g that HKI and HKII are the two major placental HK isoenzymes. HKII ac tivity was increased in placenta of insulinopenic diabetic rats. This regulation is likely to support the increase in glucose utilization an d storage characteristics of the enlarged placentae of diabetic rats. (C) 1998 W. B. Saunders Company Ltd.