Summary
Plasma concentrations of insulin, corticosterone, T3, T4 and glucose were measured
at 6 hour intervals throughout 24 hours in undisturbed, 34-day-old lean (Fa/?) and
genetically obese (fa/fa) Zucker rats, fa/fa rats had higher plasma concentrations
of insulin at all sampling times and higher plasma concentrations of corticosterone
at 0300 and 0900 hours. Neither T3 nor T4 levels differed between phenotypes at any
sampling time. Fasting for 24 hours at 34 days abolished the hyperinsulinaemia of
fa/fa rats and raised the plasma corticosterone concentrations of both phenotypes.
Before weaning there were no phenotypic differences in the plasma insulin or corticosterone
concentrations measured at two sampling times in undisturbed rats. Following an intra-gastric
glucose load however, fa/fa rats became hyperinsulinaemic compared with similarly
treated Fa/? animals.
Pancreatic insulin contents were higher in fa/fa rats at 34 days of age, but not before
weaning. Somatostatin contents of the pancreas, hypothalamus and cerebral cortex did
not differ between phenotypes at either 18 or 34 days of age. In conclusion, the elevated
plasma concentrations of insulin and corticosterone in young fa/fa rats may contribute
to their greater lipid deposition and lower protein deposition.
Key-Words
Zucker Rat
-
Plasma Hormones
-
Tissue Somatostatin
