QUICK SEARCH:   [advanced] Author: Keyword(s):
Home     Help     Feedback     Subscriptions     Archive     Search     Table of Contents

First published online May 1, 2006
Journal of Experimental Biology 209, 1964-1975 (2006)
Published by The Company of Biologists 2006
doi: 10.1242/jeb.02210

This Article Summary Full Text Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Ianowski, J. P. Articles by O'Donnell, M. J. Search for Related Content PubMed PubMed Citation Articles by Ianowski, J. P. Articles by O'Donnell, M. J.

Electrochemical gradients for Na⁺, K⁺, Cl^– and H⁺ across the apical membrane in Malpighian (renal) tubule cells of Rhodnius prolixus

Juan P. Ianowski^* and Michael J. O'Donnell

Department of Biology, McMaster University, 1280 Main Street West, Hamilton, Ontario, L8S 4K1, Canada

View larger version (28K): [in a new window]   Fig. 1. Electrochemical gradients and ion activities in (A) unstimulated and (B) 5-HT-stimulated Malpighian tubules of Rhodnius prolixus. Values for pHbath, pHi, pHlumen and luminal aK, aCl and aNa are presented as means ± s.e.m. for (N) tubules. Values in B were recorded 30 min after stimulation with 10–6 mol l–1 5-HT. Intracellular and bath activities for Na+, K+ and Cl– (italicised) and electrochemical gradients for Na+, K+ and Cl– across the basolateral membrane are taken from Ianowski et al. (Ianowski et al., 2002).

View larger version (27K): [in a new window]   Fig. 2. Effects of stimulation with 5-HT on (A) transepithelial potential (TEP), (B) basolateral membrane potential (Vbl), (C), lumen pH and(D) intracellular pH. The numbered phases of the response of transepithelial potential to 5-HT are described in the text. Open arrows indicate addition of 5-HT. Downward-pointing solid arrows indicate impalement of the cell or lumen and upward-pointing solid arrows indicate the removal of the electrode from the cell or lumen. (E,F) Values are means + s.e.m.; N=5 tubules) for lumen and intracellular pH, respectively. The asterisk indicates a significant difference (P<0.05, Student's t-test) relative to unstimulated (i.e. phase 0) tubules.

View larger version (23K): [in a new window]   Fig. 3. Effects of bumetanide on basolateral membrane potential, transepithelial potential (TEP), intracellular pH and lumen pH in 10–6 mol l–1 5-HT stimulated Malpighian tubules. Representative simultaneous recordings of TEP (A), lumen pH (B), basolateral membrane potential (Vbl) (D) and intracellular pH (E). Downward-pointing arrows indicate impalement of the cell or lumen and upward-pointing arrows indicate the removal of the microelectrode from the cell or lumen. Tubules were exposed to 10–5 mol l–1 bumetanide for the period indicated by the horizontal bar. Values are means ± s.e.m. for lumen pH (C, N=7) and intracellular pH (F, N=4) before and after bumetanide treatment. The asterisk indicates a significant difference (P<0.05, Student's t-test) between control and experimental values (means + s.e.m.).

View larger version (13K): [in a new window]   Fig. 4. Effects of amiloride 10–5 mol l–1 on fluid secretion rate, basolateral membrane potential and intracellular pH in 10–6 mol l–1 5-HT stimulated Malpighian tubules. (A) Mean fluid secretion rates (± s.e.m., N=7) are shown for tubules exposed to 10–5 mol l–1 amiloride (filled symbols) or to the vehicle alone (open symbols). The arrow indicates the addition of amiloride. (B) Representative recording of basolateral membrane potential. Downward-pointing arrow indicates impalement of the cell and upward-pointing arrow the removal of the microelectrode from the cell. Tubules were exposed to 10–5 mol l–1 amiloride for the period indicated by the horizontal bar. (C) pHi was measured before (control) and 2 min after addition of amiloride (C, N=4 tubules).

View larger version (12K): [in a new window]   Fig. 5. Effects of Na+-free saline on basolateral membrane potential and intracellular pH in 10–6 mol l–1 5-HT stimulated Malpighian tubules. Representative simultaneous recordings of basolateral membrane potential (A) and intracellular pH (B). Downward-pointing arrow indicates impalement of the cell and upward-pointing arrow the removal of the electrode from the cell. Tubules were exposed to Na+-free saline for the period indicated by the horizontal bar. (C) pHi (mean + s.e.m.) before and 2 min after exposure to Na+-free saline (N=3). The asterisk indicates a significant difference (P<0.05, paired Student's t-test).

View larger version (13K): [in a new window]   Fig. 6. Effect of 10–4 mol l–1 DIDS on fluid secretion rate, transepithelial potential (TEP), and intracellular pH in 10–6 mol l–1 5-HT stimulated Malpighian tubules. (A) Fluid secretion rate (mean ± s.e.m., N=9). Tubules were exposed to DIDS (filled symbols) at the point indicated by the arrow, or to the vehicle alone (open symbols).(B) Representative TEP recording. The first arrow indicates the addition of 5-HT 10–5 mol l–1. The second arrow indicates the time of exposure to DIDS. (C) Intracellular pH before and 2 min after addition of 10–4 mol l–1 DIDS (mean + s.e.m., N=6).

View larger version (14K): [in a new window]   Fig. 7. Effects of 10–4 mol l–1 acetazolamide in control and HCO3–-free saline on fluid secretion rate by 10–6 mol l–1 5-HT stimulated Malpighian tubules. Tubules were exposed to acetazolamide (open symbols) or to the vehicle alone (filled symbols). Arrow indicates addition of acetazolamide to tubules bathed in (A) control saline (mean ± s.e.m.; N=8) or (B) HCO3–-free saline (mean ± s.e.m.; N=8).