Pineal-pancreas interaction: pineal hormone E5 action on insulin activity.

We studied the E5 pineal hormone influence on glucidic metabolism, especially on insulin. Our investigations included the metabolic processes i.e. muscular glycogen biosynthesis and glycemia, as well as serum insulin uptake. Male rats and rabbits (lots of 5 animals) were injected (i.p. or i.v.) with E5B saline sol. (0.1 mg/ml) at various time intervals (30 min for model A or 60 min and 30 min for model B) before sacrifice. We observed the E5 influence on the insulin-induced biosynthesis of glycogen after 60 min (model A). The module (+/- % as control) of variations was positive for low and average concentrations of insulin. This findings emphasize an insulin-like activity or an increasing effect of the E5 hormone. For higher concentrations (above 900 mU insulin), an inhibitory effect was obtained. This action is time-dependent (150-270 min). The insulin-'enhanced' effect turns into an 'inhibitory' one after 330 min. An inhibitory effect of E5 on the simultaneous administration of both hormones was also obtained. We observed a significant increase of the high values (2.0-2.5 mg/ml) of the blood glucose (glycemia) at 270 min. The glycemia values distribution presupposes a hyperglycemic-type activity of the E5 hormone. We recorded an increase of the plasma insulin (at 30 min), followed by its decrease (at 60 min). The decrease goes on up to 240 min. The insulin values tend to rise again to the initial level up to 720 min. (model A and B). These observations suggest that E5 activity on insulin is acute (at less than 30 min) and effective for longer than 7 hours.(ABSTRACT TRUNCATED AT 250 WORDS)