The effect of parenteral and enteral nutrition on portal and systemic immunoreactivities of gastrin, glucagon and vasoactive intestinal polypeptide (VIP)

To compare the effect of parenteral with enteral nutrition on gastroentero-pancreatic hormones, hypercaloric and hypocaloric nutrient preparations, commonly used clinically, were administered to rats either through cannulae in the jugular vein or gastrostomies. Control rats were fed orally ad libitum. Portal and aortic plasma was collected for radioimmunoassay with antibodies to C-terminal regions of gastrin and glucagon and to N-terminal-to-central regions of glucagon and VIP. Levels of all immunoreactivities were significantly lower in aortic than portal plasma. Apparent clearance of glucagon and gastrin by liver or lung both was enhanced by administration of the hypercaloric nutrient intravenously. Only intragastric hypercaloric nutrition maintained levels of VIP immunoreactivity close to those of control rats. Intragastric administration of either preparation appeared to maintain adequate levels of gastrin. Differences in the levels of glucagon immunoreactivities may be related to the stimulatory effects of metabolites in the lower gut and pancreas.

The role of postnatal age and magnesium on parathyroid hormone responses during "exchange" blood transfusion in the newborn period

One hundred and eight "exchange" blood transfusions were done on 61 newborn infants. Baseline serum PTH concentrations and the PTH rise in response to citrate-induced hypocalcemia were studied. Baseline PTH values increased with postnatal age, particularly after the first three days of life. The acute response of PTH to citrate-induced hypocalcemia appears within ten minutes following the initiation of exchange transfusion and was shortlived in spite of further decline of serum ionized calcium. The dominant effect of postnatal age over gestational age was demonstrated: postnatally older but gestationally less mature infants exhibited greater responsiveness than postnatally younger, but gestationally more mature, infants. The PTH response during exchange transfusion was blunted in hypomagnesemic infants. Since lower serum magnesium concentrations were also present during the first three days of life, a separate effect of serum magnesium concentrations on parathyroid responsiveness cannot be ruled out in this study.

Circulating immunoreactivities of gastrin, glucagon and VIP after jejuno-ileal bypass

Seven Sprague-Dawley rats (404-440 g) underwent a 90% jejuno-ileal bypass (JIB); the functional loop consisted of 1/3 ileum and 2/3 jejunum with the bypassed loop being anastomosed to the ascending colon. Seven control rats were sham-operated. After 35 days, the rats were fasted 18 hours and venous blood was collected. Immunoreactivity of gastrin, measured with an antibody binding equally to G17 and G34, was higher in the plasma of the JIB (256 +/- 55 SEM pg/ml) than control (85 +/- 9 pg/ml) rats. This agrees with recent human studies but is in conflict with results in less mature rats. VIP levels were not significantly different. Glucagon-like immunoreactivity measured with antibodies specific for the C- and N-terminal regions of the hormone, respectively, were also higher in the JIB (510 +/- 40 and 129 +/- 15 pg/ml) rats.