Effects of chronic hypoxia on electrogenic transport and transport-related oxygen consumption in rat distal colon.

The distal colon epithelium of rats submitted to chronic hypoxia shows higher short-circuit current (Isc) which, unlike non-hypoxic rat epithelium, has an amiloride-sensitive component despite low serum aldosterone levels. Isc and oxygen consumption (QO2) were simultaneously measured in mucosae from rats submitted to 0.5 atm for 10 days and from control rats in a modified Ussing chamber. Hypoxia increased Isc but not QO2. The slope of the regression line between Isc and QO2 reduction after ouabain addition was decreased in epithelia from hypoxic rats (P = 0.03). Chloride secretion blockade reduced Isc and QO2 in both groups, while sodium channel blockade did so only in the hypoxic group. Dual blockade in hypoxic rat epithelia caused correlated (P = 0.0025) additive decreases in Isc and QO2. Presented results suggest that chronic hypoxia induces an improved coupling between QO2 and electrogenic ion transport, and electrogenic sodium absorption despite low aldosterone levels.

Single-channel response of hamster oocytes to fertilization with homologous spermatozoa.

Electrophysiological events occur early after fertilization, along with changes in intracellular Ca2+ concentration. Passive electrical parameters were determined in golden hamster oocytes by whole cell patch-clamp method. In separate experiments the effect of 4-aminopyridine on resting oocytes was tested. The single-channel patch clamp configuration was employed to assess the electrical response to fertilization with homologous sperm. Structure of oocytes submitted to patch clamp was evaluated with scanning electron microscopy and found to be preserved. Oocyte diameter was 70.2 +/- 2.2 microm; their resting parameters were: membrane potential 23.8 +/- 0.8 mV; total membrane specific resistance 519.1 +/- 94.6 ohms.cm2, and specific capacity 0.99 +/- 0.03 microF.cm(-2). Total membrane current was decreased by 42 % by 4-aminopyridine. Control oocytes and oocytes exposed to sperm differed in their membrane currents in response to a voltage ramp clamping membrane potential from - 100 mV to + 100 mV. In both cases, currents were largest at the most negative potentials, but sperm-exposed oocytes had larger currents. Additionally, while in control oocytes the current was inward at negative potentials but outward at positive potentials, in the presence of spermatozoa oocytes was inward within the whole voltage range tested. This latter current may represent Ca2+ entry.

Single-channel response of hamster oocytes to fertilization with homologous spermatozoa

Electrophysiological events occur early after fertilization, along with changes in intracellular Ca2+ concentration. Passive electrical parameters were determined in golden hamster oocytes by whole cell patch-clamp method. In separate experiments the effect of 4-aminopyridine on resting oocytes was tested. The single-channel patch clamp configuration was employed to assess the electrical response to fertilization with homologous sperm. Structure of oocytes submitted to patch clamp was evaluated with scanning electron microscopy and found to be preserved.Oocyte diameter was 70.2 ± 2.2 µm; their resting parameters were: membrane potential 23.8 ± 0.8 mV; total membrane specific resistance 519.1 ± 94.6 Ù.cm2, and specific capacity 0.99 ± 0.03 µF.cm-2. Total membrane current was decreased by 42 % by 4-aminopyridine.Control oocytes and oocytes exposed to sperm differed in their membrane currents in response to a voltage ramp clamping membrane potential from - 100 mV to + 100 mV. In both cases, currents were largest at the most negative potentials, but sperm-exposed oocytes had larger currents. Additionally, while in controloocytes the current was inward at negative potentials but outward at positive potentials, in the presence of spermatozoa oocytes was inward within the whole voltage range tested. This latter current may represent Ca2+ en try

Single-channel response of hamster oocytes to fertilization with homologous spermatozoa

Electrophysiological events occur early after fertilization, along with changes in intracellular Ca2+ concentration. Passive electrical parameters were determined in golden hamster oocytes by whole cell patch-clamp method. In separate experiments the effect of 4-aminopyridine on resting oocytes was tested. The single-channel patch clamp configuration was employed to assess the electrical response to fertilization with homologous sperm. Structure of oocytes submitted to patch clamp was evaluated with scanning electron microscopy and found to be preserved.Oocyte diameter was 70.2 ± 2.2 Am; their resting parameters were: membrane potential 23.8 ± 0.8 mV; total membrane specific resistance 519.1 ± 94.6 Ù.cm2, and specific capacity 0.99 ± 0.03 AF.cm-2. Total membrane current was decreased by 42 % by 4-aminopyridine.Control oocytes and oocytes exposed to sperm differed in their membrane currents in response to a voltage ramp clamping membrane potential from - 100 mV to + 100 mV. In both cases, currents were largest at the most negative potentials, but sperm-exposed oocytes had larger currents. Additionally, while in controloocytes the current was inward at negative potentials but outward at positive potentials, in the presence of spermatozoa oocytes was inward within the whole voltage range tested. This latter current may represent Ca2+ en try(AU)

Single-channel response of hamster oocytes to fertilization with homologous spermatozoa

Electrophysiological events occur early after fertilization, along with changes in intracellular Ca2+ concentration. Passive electrical parameters were determined in golden hamster oocytes by whole cell patch-clamp method. In separate experiments the effect of 4-aminopyridine on resting oocytes was tested. The single-channel patch clamp configuration was employed to assess the electrical response to fertilization with homologous sperm. Structure of oocytes submitted to patch clamp was evaluated with scanning electron microscopy and found to be preserved.Oocyte diameter was 70.2 ± 2.2 Am; their resting parameters were: membrane potential 23.8 ± 0.8 mV; total membrane specific resistance 519.1 ± 94.6 Ù.cm2, and specific capacity 0.99 ± 0.03 AF.cm-2. Total membrane current was decreased by 42 % by 4-aminopyridine.Control oocytes and oocytes exposed to sperm differed in their membrane currents in response to a voltage ramp clamping membrane potential from - 100 mV to + 100 mV. In both cases, currents were largest at the most negative potentials, but sperm-exposed oocytes had larger currents. Additionally, while in controloocytes the current was inward at negative potentials but outward at positive potentials, in the presence of spermatozoa oocytes was inward within the whole voltage range tested. This latter current may represent Ca2+ en try(AU)