Effects of hepatic portal infusion of hypertonic saline on glucagon response to exercise

The present study was conducted to evaluate the influence of a hepatic port al infusion of hypertonic saline on the metabolic and hormonal responses to exercise. Adrenodemedullated male rats were studied at rest or after 30 mi n of treadmill exercise (26 m/min, 0% grade). Three groups of rats were inf used continuously at a rate of 52 mu L/min with one of the following random ly assigned conditions: hypertonic 3.6% NaCl (P3.6% NaCl) or 1.8% NaCl (P1. 8% NaCl) infused into the hepatic portal vein, and hypertonic 3.6% NaCl (J3 .6% NaCl) infused into the jugular vein. One group of rats received no infu sion (SHAM). The infusions of hypertonic NaCl into the portal or the jugula r site resulted in a significant (p < 0.05) increase in peripheral concentr ation of Na+, Cl-, and osmolality at rest and after exercise. The antidiure tic hormone (ADH) concentration was significantly (p < 0.05) increased by t he P3.6% NaCl and J3.6% NaCl infusions at rest and after exercise. Exercise caused a significant (p < 0.05). decrease in liver glycogen content, perip heral and portal plasma glycemia, and insulinemia regardless of the differe nt types and sites of infusions. However, the peripheral glucagon response to exercise was significantly (p < 0.05) increased only when hypertonic sal ine (1.8 or 3.6%) was infused into the portal vein. Portal and peripheral l actate concentrations at rest and after exercise were significantly (p < 0. 01) higher in P3.6% NaCl than in all other groups. It is concluded that at 30-min hypertonic saline infusion into the hepatic portal vein does not spe cifically influence the insulin response at rest and after exercise, but th at glucagon response to exercise is increased by such an infusion. (C) 1999 Elsevier Science Inc.