Diapedesis of thrombocytes from capillary into the intercellular space of interscapular brown adipose tissue and their increase by Ca-Sandoz

Abstract

Diapedetic capacity of the rat thrombocytes to leave capillaries of the interscapular brown adipose tissue (IBAT) and infiltrate the interstitium has been observed by conventional electron-microscopy. Thrombocytes that reach IBAT interstitium are morphologically completely different from lumenary ones. The interstitial thrombocyte has a prominet head region (1.51x2.12 pm) and very long phylopodium (3.43 pm). Experimental conditions which induced drastic changes in morphology of interstitial thrombocytes were: sucrose overfeeding (10% over 2 days); a 24 hour starving after sucrose overfeeding and Ca-Sandoz drinking (480 mg/L ca2+ during 2 days). The thrombocytes in the IBAT interstitium can be classified,as activated according to: a) pseudopode extension; b) swollen open canalicullar system (OCS); c) endocytosis via coated pits and vesicles; and d) structural changes in a granules excreted to the interstitium through OCS. In the IBAT interstitium of 24-hour starved rats after sucrose overfeeding, a thrombocytic layer was observed. It was suggested that thrombocyte adrenalin, stored in dense bodies, was selectevely included in the IBAT supply without mediation of the central nervous system.