The secretory dynamics of the CHH-producing cell group in the eyestalk of the crayfish, Astacus leptodactylus, in the course of the day/night cycle

Abstract

The secretory dynamics of the Crustacean Hyperglycemic Hormone (CHH)-producing cells in the eyestalk of the crayfish Astacus leptodactylus were studied during the daily cycle (12 h light/12 h dark). The different secretory stages of individual cells were determined by means of immunocytochemistry combined with morphometric analysis at the light-microscopic level. The data obtained were correlated with the 24-h rhythmicity of blood glucose concentration. The results suggest the following hypothesis. The synthetic activity of the CHH cells receives a stimulus 2 h before the beginning of the dark period, resulting in a pronounced transfer of CHH granules into the axons. These CHH granules reach the axon terminals after the onset of the dark period. At that time a burst of exocytotic activity occurs, causing a strong release of CHH into the hemolymph. Four hours later this CHH release results in hyperglycemia. The same process, though with less intensity, is repeated and causes a second smaller glucose peak at the beginning of the light period.