Quantitative histochemistry of the angiotensinase A (APA) in the renal glomeruli of rats after stimulation of the renin‐angiotensin system,

Abstract

Quantitative histochemical measurements is concluded that glomerular M A activities of aminopeptidase A ( M A , angiotensinase A) correspond to the reninlangiotensin plasma were done kinetically in the kidney glomeruli levels and that the fast changes of APA activof rats after short-term experiments (treat-ities are well demonstrable by kinetic densiment with furosemide as well as captopril for tometric measurements in situ. 2, 4, and 6 h). The APA activities increased after treatment with furosemide or captopril.Highest activities were determined after 4 h using furosemide and 6 h using captopril. I t Key terms: Quantitative histochemistry, aminopeptidase A, kidney glomeruli Microdensitometric (microphotometric) procedures make it possible to determine enzyme activities in tissue sections at cellular level (1,2,4,8,9,11,20,24). The combination of microdensitometers (microphotometers) with computers allows kinetic determinations of enzyme activities in tissue sections, and therefore maximal enzyme activities now can be recorded in the range of linear kinetics (11,22,23).The application of such quantifying procedures on proteinase histochemistry in the kidney (8,(13)(14)(15) has shown that a special aminopeptidase in the glomerulus and the brush border of the proximal tubule, namely the membrane-bound aminopeptidase A (APA; 12, 17), is the socalled angiotensinase A (13~5). This peptidase cleaves N-terminal aspartic acid from angiotensin I and I1 (ANG I, II) and is to be considered as a component of the reninangiotensin system (RAS) in the kidney.In the present quantitative histochemical study we used short-term experiments in rats with furosemide and captopril, which stimulate the RAS in different ways (6,10), to show that glomerular APA activities change rapidly in accordance with the condition of the RAS. It is possible to record early changes in a hormonal system using quantitative histochemistry. MATERIALS AND METHODS Animal MaterialThe investigations were performed in a total of 70 adult male Wistar rats of our own breeding. Before the experiments (see below) the animals were selected according to bodyweight (BW, 285-310 g) and age (75 to 95 cl). The animals were housed in Makrolori cages at 21 2°C with light-dark changes a t 12-h intervals. Tap water and standard altromin feed (TPF 1320) were given ad libitum.For the experiments the animals were divided into five groups: Group I consisted of 15 rats that received a single intraperitoneal (i.p.) injection of 10 mg/100 g BW furosemide (LasixR, 250 mg from Hoechst). Five rats each were killed 2,4, and 6 h after the beginning of the treatment. Group I1 consisted of 15 rats that received a single i.p. injection of 0.1 mg/100 g BW captopril(O.3 mg dissolved in 1 ml 0.85% NaCl solution; captopril was a gift of von Heyden company). Five rats each were killed 2,4, and 6 h after the beginning of the treatment. Group I11 (controls for group I and 11) consisted of 15 rats that received a single i.p. injection of 0.33 mVlOO g BW 0.85% NaCl solution. Five rats each were ...

A nephritogenic rat monoclonal antibody to mouse aminopeptidase A. Induction of massive albuminuria after a single intravenous injection.

“…In the glomerulus, binding of angiotensin II to its receptor on mesangial cells induces contraction of these cells influencing the glomerular capillary surface area available for filtration and consequently the glomerular capillary uhrafiltration coefficient (Kf) (51). At this moment, it is thought that APA on glomerular epithelial cells may bind and rapidly inactivate angiotensin II delivered to the glomerulus and then filtered via the capillary wall (52,53).…”