Impairment of glucose tolerance in yellow (Avy/A) (BALB/c X VY) F-1 hybrid mice by hyperglycemic peptide(s) from human pituitary glands.

A fraction of human pituitary extract containing low molecular weight peptide(s) was found to impair glucose tolerance in obese yellow (Avy/A) (BALB/c X VY) F-1 hybrid female mice. In these mice, purified human GH was not hyperglycemic. Glucose tolerance of untreated yellow mice was somewhat less impaired than that of untreated ob/ob mice, and priming with dexamethasone was not required to elicit impairment of glucose tolerance. The lean agouti (A/a) littermates of the yellow mice did not respond to the hyperglycemic peptide(s), suggesting that an insulin-resistant animal is required for assay of the pituitary hyperglycemic peptide(s). Plasma insulin levels of the obese yellow mice treated with the hyperglycemic peptide(s) were significantly decreased compared to those of saline-treated controls. No decrease in plasma insulin was observed in the similarly treated lean agouti mice. The study demonstrated that the yellow Avy/A (BALB/c X VY) F-1 hybrid mouse is a suitable animal for investigation of the physiological mechanism of action of the pituitary hyperglycemic peptide(s).