La régression du mésonéphros chez l’embryon de poulet

Abstract

ABSTRACT The regression of the mesonephros in the chick embryo: a study of acid phosphatase and cathepsin activity analysed biochemically, histochemically, and by electron microscopy Cathepsin and acid phosphatase activity and total nitrogen were determined in homogenates of mesonephros during growth (at 14 days) and regression (at 21 days). The loss of total nitrogen in this period is as much as 62%. Specific cathepsin activity, expressed as μg casein destroyed per hour per μg total nitrogen, does not change much. The increase of 19·4% observed was not significant. Specific acid phosphatase activity, expressed as 10−3μM phosphate liberated per hour per μg of total nitrogen, increases appreciably during regression. The increase between the 14th and 21st day of incubation is by 114·4%. The absolute levels of cathepsin and acid phosphatase activity are reduced during mesonephric regression by 57·6 % and 24·7 % respectively. Fractionation showed that these enzymes were solubilized during mesonephric regression. The soluble component increased by 28·4% in the case of cathepsin and by 44% in the case of acid phosphatase. Histochemical preparations for acid phosphatase and for non-specific esterases showed that these enzymes were most abundant in the apical part of the cells of the proximal tubules (secretory region with brush border). During regression, the intensity of the acid phosphatase reaction increased and large granules appear in the cells of the tubules, while the connective tissue shows cells with inclusions which could be macrophages. Electron microscopy revealed important changes in the cells of the secretory tubules during regression. On the one hand mitochondria degenerate while on the other hand cytoplasmic inclusions appear, among which are dense membranous bodies reacting positively for acid phosphatase. Mesonephric regression is compared with that of other larval and embryonic organs and its mechanism is discussed.