BLOOD-GLUCOSE LEVELS IN INTACT AND HYPOPHYSECTOMIZED RIVER LAMPREYS (LAMPETRA-FLUVIATILIS L) TREATED WITH INSULIN, STRESS, OR GLUCOSE, BEFORE AND DURING PERIOD OF SEXUAL-MATURATION

Glucose concentration in peripheral blood increased transiently in intact male and female river lampreys (Lampetra fluviatilis L.) at the time of spermiation and ovulation, from 20-30 mg/100 ml to about 35 mg/100 ml in spite of constant conditions (11.degree. C and darkness). A transfer of lampreys from 11.degree. to 6 and 16.degree. C caused hyperglycemia after 24 h, but after 1 wk blood glucose concentrations were not different from the initial values. Various insulin preparations were used (Ultralente, zinc-protamin-insulin, Actrapid and an acid solution of beef insulin) in doses from 0.03-0.8 IU/animal (about 60 g). The minimum dose causing hypoglycemia (after 24 h) is about 0.04 IU. With 0.1 IU Actrapid maximal response was found between 8 and 24 h after the injection. Insulin had only slightly greater and more prolonged action in hypophysectomized than in intact river lampreys, both before and during the period of sexual maturation. The pro- and mesoadenohypophysis thus exert only a slight anti-insulin effect. Insulin caused a dose-related increase in length of the body in both intact and hypophysectomized lampreys. The procedure for blood sampling, especially the anesthesia, caused hyperglycemia after 24 h in sexually immature and in hypophysectomized lampreys, slightly lower and less long lasting in hypophysectomized lampreys. Maximal response was found after about 2 h. The pro- and mesoadenohypophysis thus are of little importance for the stress hyperglycemia. In sexually mature lampreys the stress hyperglycemia was normalized much more rapidly than in immature lampreys or hypophysectomized lampreys. Hyperglycemia induced by exogenous glucose was similarly normalized more rapidly. The high level of blood glucose at sexual maturation is thus a well-regulated phenomenon. The response to insulin was not affected even by a great stress (long time of anesthesia) at the time of injection.