ENZYME HISTOCHEMISTRY AND FUNCTIONAL DIFFERENTIATION OF THE RAT METANEPHROS

Abstract

Since histochemistry was introduced into the study of animal tissues, many investigators have localized the site of activity of a number of enzymes in both the developing kidney the adult kidney. Moog (1944) demonstrated the presence of alkaline phosphatase in the tubules of the pronephros of the white leghorn chick embryo from the 4th day of incubation, Junqueira (1952) made a similar observation in the tubules of the pronephros of the New Hampshire Red chick embryo. Baxter (1950) localized the site of activity of alkaline phosphatase histochemically in both the mesonephros and metanephros of human embryos. Many other investigators have localized the activity of different enzymes in the kidney of different animals. Attempts have been made in the past to correlate the enzyme histochemistry of the kidney with the function of the organ. Thus Kay (1926) in a study of kidney phoshatases suggested that alkaline phosphatase in the brush border of the proximal tubules, rather than acid phosphatase found in the cytoplasm of the cells of the tubules, may have a functional activity of hydrolysing organic phosphoric esters, filtered by the glomerulus from the circulating blood plasma. Wilmer (1944) gave no supporting evidence to his suggestion that renal phosphatases may play a role in the re-absorption of sugar by dephosphorylating the hexose-phosphates in the kidney. Pinkstaff, Sandler and Bourne (1962) localized the activity of adenosine triphosphatase in the pre-glomerular segment of the urinary tubule of matanephros from 20-day rat embryos. He suggested that adenosine triphosphatase as well as other phosphatases may function in the renal transport mechanisms. In a review of histochemical results on embryo of some birds and mammals, Blio Borghese (1957) wrote: "It is perhaps tempting to try to follow the developmental processes, starting with cleavage, through the first phases of organogenesis during the morphological development of the organs until their function begins, and to introduce histochemical data at every step of development. Thus it would be possible to know at what stage of development a certain substance first appears, what chemical changes in correlation with the degrees of differentiation of the organs are, and how the chemical structure is related to the beginning of function and so on....." This study has introduced histochemistry, biochemistry and autoradiography in the study of the differentiation of the rat metanephros from the 13 day of gestation of the embryo. This is the stage of gestation when the metanephros is first formed. Such enzymes as phosphorylase, uridine-diphosphate glucose transferase, glucose-6-phosphatase have been studied both histochemically and biochemically. Glycogen levels have also been estimated quantitatively. Lysosomal enzymes such as leucine amino peptidase, B-glucuronidase, and acid phosphatase have been studied histochemically. Oxidative enzymes such as glucose-6-phosphate dehydrogenase, 6-phospho-gluconic dehydroganase, succinic dehydrogenase, glutamic dehydrogenase and lactic dehydrogenase have also been studied histochemically. Akaline phoshatase activity was also studied histochemically. Autoradiography with tritiated para-amino hippuric acid was introduced at every stage of development of the metanephros to study the onset of function. The results show the chronology of enzymogenesis in the rat metanephros and the stage of onset of function. An attempt was made to correlate the enzymogenesis of the rat metanephros with the metabolic processes in the metanephros as well as the probable parts played by these enzymes in the functional and morphological differentiation of the rat metanephros.