Serum Immunoreactive Insulin in the Hypophysectomized Dog.
Effect of Cortisol Replacement Therapy[* ]

Abstract

Serum immunoreactive insulin (IRI) concentrations were measured in hypophysectomized and normal dogs, during an i.v. glucose tolerance test (GTT) (1 g glucose per kg body weight). Animals were awaken and as quiet as possible, after 16-18 hour fast. Two blood samples were withdrawn by venipuncture, in postabsorptive state, within 1 hr before the glucose load. Six blood samples were taken after the glucose injection (5, 15, 25, 45, 60 and 90 minutes after glucose load). Hypophysectomized dogs received Cortisol therapy, subcutaneously (1 mg/kg body wt./day, for 14-16 days, in saline), and the glucose tolerance tests with simultaneous measurement of IRI concentration in serum were performed again. The last Cortisol injection was given 1 hour before glucose load.

Blood glucose and serum IRI concentration were measured according to Somogyi and Nelson, and Morgan and Lazarow technique, respectively.

Glucose tolerance test was normal in dogs after hypophysectomy, whether before or after Cortisol treatment. Serum IRI concentration was not changed after hypophysectomy and/or Cortisol treatment in dogs, in post-absorptive state. Serum IRI concentration curve after glucose injection was lower than normal in uninjected hypophysectomized dogs, cortisol therapy leading it into normality.

Key words

Hypophysectomized Dogs - Cortisol Therapy - Serum Immunoreactive Insulin - Insulin-Glucose Ratio

1 This work was partially supported by research grant No. 2304-a from the "Consejo Nacional de Investigaciones Científicas y Técnicas" (República Argentina) and by a research contract from the "Comisión Nacional de Energía Atómica" (Argentina).

1 This work was partially supported by research grant No. 2304-a from the "Consejo Nacional de Investigaciones Científicas y Técnicas" (República Argentina) and by a research contract from the "Comisión Nacional de Energía Atómica" (Argentina).