TY - JOUR
T1 - Na(+)‐ and H(+)‐gradient‐dependent transport of alpha‐aminoisobutyrate by luminal membrane vesicles from rabbit proximal tubule.
AU - Jessen, Henrik
AU - Vorum, Henrik
AU - Jørgensen, Karl Evald
AU - Sheikh, M. Iqbal
PY - 1991/5/1
Y1 - 1991/5/1
N2 - 1. The characteristics of renal transport of alpha‐aminoisobutyrate (AIB) by luminal membrane vesicles isolated from either the proximal convoluted part (pars convoluta) or the proximal straight part (pars recta) of rabbit proximal tubule were investigated. 2. Transport of AIB in vesicles from pars convoluta was mediated by both Na(+)‐dependent and Na(+)‐independent systems, which in the presence of an inwardly directed H+ gradient can drive the uphill transport of AIB into these vesicles. 3. By contrast, in luminal membrane vesicles from pars recta, transient accumulation of AIB was only dependent on Na+. Lowering pH without a H+ gradient (pHi = pH0 = 5.5) completely abolished the Na(+)‐dependent transient accumulation of AIB in these vesicle preparations. 4. Attempts to determine the stoichiometry of both the Na(+)‐AIB and H(+)‐AIB transporters located in these two segments of proximal tubule suggested that one Na+ and one H+ ion may be involved in the transport of AIB. 5. Sodium‐dependent uptake of AIB in vesicles from pars convoluta was competitively inhibited by L‐serine and L‐phenylalanine, whereas the presence of L‐proline, L‐alanine and glycine had no significant effect. By contrast, the H(+)‐gradient‐dependent uptake of AIB was drastically reduced (30% of the control value) by L‐proline, L‐alanine and glycine, while L‐serine and L‐phenylalanine had no significant effect. 6. On the other hand, pars recta vesicles exhibited a different transport specificity. L‐Phenylalanine, L‐serine, L‐alanine and glycine, but not L‐proline competitively inhibited the uptake of AIB, providing evidence for the existence of a common transport system for AIB, L‐phenylalanine, L‐serine, L‐alanine and glycine in this segment of rabbit proximal tubule.
AB - 1. The characteristics of renal transport of alpha‐aminoisobutyrate (AIB) by luminal membrane vesicles isolated from either the proximal convoluted part (pars convoluta) or the proximal straight part (pars recta) of rabbit proximal tubule were investigated. 2. Transport of AIB in vesicles from pars convoluta was mediated by both Na(+)‐dependent and Na(+)‐independent systems, which in the presence of an inwardly directed H+ gradient can drive the uphill transport of AIB into these vesicles. 3. By contrast, in luminal membrane vesicles from pars recta, transient accumulation of AIB was only dependent on Na+. Lowering pH without a H+ gradient (pHi = pH0 = 5.5) completely abolished the Na(+)‐dependent transient accumulation of AIB in these vesicle preparations. 4. Attempts to determine the stoichiometry of both the Na(+)‐AIB and H(+)‐AIB transporters located in these two segments of proximal tubule suggested that one Na+ and one H+ ion may be involved in the transport of AIB. 5. Sodium‐dependent uptake of AIB in vesicles from pars convoluta was competitively inhibited by L‐serine and L‐phenylalanine, whereas the presence of L‐proline, L‐alanine and glycine had no significant effect. By contrast, the H(+)‐gradient‐dependent uptake of AIB was drastically reduced (30% of the control value) by L‐proline, L‐alanine and glycine, while L‐serine and L‐phenylalanine had no significant effect. 6. On the other hand, pars recta vesicles exhibited a different transport specificity. L‐Phenylalanine, L‐serine, L‐alanine and glycine, but not L‐proline competitively inhibited the uptake of AIB, providing evidence for the existence of a common transport system for AIB, L‐phenylalanine, L‐serine, L‐alanine and glycine in this segment of rabbit proximal tubule.
U2 - 10.1113/jphysiol.1991.sp018544
DO - 10.1113/jphysiol.1991.sp018544
M3 - Journal article
C2 - 2061829
AN - SCOPUS:0025905339
SN - 0022-3751
VL - 436
SP - 149
EP - 167
JO - The Journal of Physiology
JF - The Journal of Physiology
IS - 1
ER -