Characterization of acidification in the cortical and medullary collecting tubule of the rabbit.

Abstract

A B S T R A C T Ouabain and lithium decrease acidification in open-circuited bladders by eliminating the electrical gradient favoring acidification. The effect of ouabain and lithium on acidification in cortical and medullary collecting tubules derived from starved New Zealand white rabbits was studied by using the techniques of isolated nephron microperfusion and microcalorimetric determination of total CO2 flux. Bath and perfusion solutions were symmetric throughout all studies, and solutions contained 25 meq of bicarbonate and were bubbled with 93.3% 02/6.7% CO2 gas mixtures. In cortical collecting tubules, ouabain (108 M) addition to bath resulted in a decrease in both potential difference (PD), from -16.4 to -2.2 mV (P < 0.001), and total CO2 flux (JTCO,), from +6.0 to 1.5 pmol/mm per min (P < 0.005). In medullary collecting tubules neither PD nor JTCO2 changed with the addition of ouabain in either 108 or 10' M concentration. Replacement of 40 mM NaCl with 40 mM LiCl in both perfusate and bath in cortical collecting tubules resulted in decreases in both PD, from -11.6 to 0.4 mV (P < 0.005), and JTC02 from +10.8 to +4.2 pmol/mm per min (P < 0.025). This substitution had no effect on medullary collecting tubules. When control flux rates were plotted against animal bladder urine pH, both medullary and cortical tubules showed good inverse correlation between these variables, with higher values of flux rate for the medullary tubules. The data support a role for transepithelial PD in acidification in the cortical collecting tubule and also suggest that both cortical and medullary segments of the collecting tubule participate Portions of this work were presented at the American Society of Nephrology

Dual regulatory mechanisms of proton transport in rat papillary collecting duct cells in culture.

“…In contrast, KLEINMAN et al (1987) were unable to demonstrate significant Na +-H + exchange activity at resting state under similar experimental conditions. An ATP-driven proton pump has been described in toad urinary bladder (AL-AWQATI et al, 1977), bovine renal medulla (CLUCKS and AL-AWQATI, 1984), rat renal cortex and medulla, rabbit medullary collecting duct cells (LAsKI and KURTZMAN, 1983;LOMBARD et al, 1983;STONE et al, 1983;SABOLIC and BURCKHARDT, 1986;ZEIDEL et al, 1986), and human renal medulla (DIAz-DIAz et al, 1986). The characteristics of this proton pump have been characterized as follows: l) dependent on ATP; 2) electrogenic; 3) stimulated by anion; 4) insensitive to vanadate, ouabain, and oligomycin; and 5) inhibited by dicyclohexylcarbodiimide (DCCD) and sulfadyl agents.…”

“…It is well known that the acidification occurs in several distinct distal nephron segments including the distal covoluted tubule, and the connecting tubule, the cortical collecting tubule, and the medullary and papillary collecting ducts (MCKINNEY and BURG, 1977;LUcci et al, 1982;LASKI and KURTZMAN, 1983;LOMBARD et al, 1983;STONE et al, 1983). Recently, direct evidence of hydrogen ion secretion has been obtained by studies conducted in segments of the rabbit and the rat collecting system by in vitro microperfusion (MCKINNEY and BURG, 1977;LASKI and KURTZMAN, 1983;LOMBARD et al, 1983;STONE et al, 1983) or by using a pH-sensitive dye in suspended cells (ZEIDEL et al, 1986). The capacity of proton secretion shows segmental differences in the collecting ducts.…”

“…The capacity of proton secretion shows segmental differences in the collecting ducts. The cortical collecting tubule from the rabbit possesses a low capacity for acidification (MCKINNEY and BURG, 1977;LASKI and KURTZMAN, 1983;LOMBARD et al, 1983). The outer medullary collecting tubule from the rabbit and rat secretes proton at a higher rate (LASKI and KURTZMAN, 1983;LOMBARD et al, 1983;STONE et al, 1983;ATKINS and BURG, 1985).…”

“…The cortical collecting tubule from the rabbit possesses a low capacity for acidification (MCKINNEY and BURG, 1977;LASKI and KURTZMAN, 1983;LOMBARD et al, 1983). The outer medullary collecting tubule from the rabbit and rat secretes proton at a higher rate (LASKI and KURTZMAN, 1983;LOMBARD et al, 1983;STONE et al, 1983;ATKINS and BURG, 1985). Although recent data also support the existence of an ATP-dependent proton secretion in the outer medullary collecting duct of the rabbit examined by a pH-sesitive dye in cell suspensions in vitro (ZEIDEL et al, 1986), the mechanisms of proton secretion in the collecting system remain unclear.…”

Adaptive changes of H+ and/or bicarbonate transport in chronic metabolic acidosis: Its quantitative evaluation by using isolated perfused kidney.

“…The adaptation to the chronic acid-base change was noted in the proximal convoluted tubules of the rat and the rabbit (Cogan et al 1979;Tsai et al 1984), the rat distal convoluted tubules (Lucci et al 1982), the rabbit cortical and medullary collecting ducts (McKinney and Burg 1977; Laski and Kurtzman 1983;Lombard et al 1983) and the rat papillary collecting ducts (Ulrich and Papavassiliou 1981), in addition to the rat distal nephron (Terao and Tannen 1981; Kornandakieti et al 1983). The present results do not provide any insight into the localizations of the adaptation in the nephron and the relative contribu- Lions of those segments to it.…”