Effect of glandular kallikrein on distal nephron HCO-3 secretion in rats and on HCO-3 secretion in MDCK cells

PATRICIA G. VALLES; SUSAN EBNER; WALTER MANUCHA; LUIS GUTIERREZ; MARCOS MARIN-GREZ

AMERICAN JOURNAL OF PHYSIOLOGY-RENAL PHYSIOLOGY - (Print)

American Physiological Society,

Lugar: Bethesda, Md; Año: 1997 vol. 273 p. 807 - 816

0363-6127

Renal kallikrein is localized in the connecting tubule cells and secreted into the tubular fluid at late distal nephron segments. The present experiments were performed to fur­ther test the hypothesis that renal kallikrein reduces bicarbon­ate secretion of cortical collecting duct (CCD). The effect of orthograde injections of pig pancreatic kallikrein (1 or 3 pg/ml) into the renal tubular system was investigated. Urine fractions (Fr) were collected after a 2-min stop flow. Changes in the urine fraction with respect to those in free-flow urine samples (Ft) were related to the respective polyfructosan inutest ratio. Renal kallikrein activity (Fr:Ff kallikreinl/Ff polyfructosan) increased significantly in the first two urine fractions collected after glandular kallikrein administra­tion (kallikrein, 1 pg/ml, P < 0.05; kallikrein, 3 pg/ml, P < 0.01). HCO-3 secretion of collecting ducts was significantly reduced dose dependently by orthograde and also reduced by retrograde pig pancreatic kallikrein administration. Release of kinins into the fractions was not affected by the retrograde kallikrein injection, even though the kallikrein activity in­creased considerably (2.26 ± 0.2 vs. 1.55 ± 0.2, P < 0.05). Adequacy of retrograde injections for delivering substances to the CCD was demonstrated by injecting colloidal mercury and detecting the appearance of this mercury in the renal cortex by transmission electron microscopy. The integrity of the renal tissue after a retrograde ureteral injection was confirmed by scanning electron microscopy. These results confirm and extend previous data (M. Marin-Grez and P. Vallés. Renal Physiol. Biochem. 17: 301-306, 1994; and M. Marin-Grez, P. Vallés, and P. Odigie. J. Physiol. 488: 163-170, 1995) showing that renal kallikrein reduces bicarbonate secretion at the CCD, probably by inhibiting HCO-3 trans­ported by a mechanism unrelated to its kininogenase activity. Support for this assessment was obtained in experiments festing the effect of kallikrein on the luminal bicarbonate secretion of a subpopulation of Madin-Darby canine kidney cells capable of extruding the anion. Kallikrein inhibited HCO-3/Cl- exchange, and the degree of inhibition was dose dependent. This inhibition occurred in the absence of kinino­gen in the bathing solution.