MEMBRANE POTENTIAL MEASUREMENTS IN ISLETS OF LANGERHANS FROM ob/ob OBESE MICE SUGGEST AN ALTERATION IN [Ca²⁺]_i‐ACTIVATED K⁺ PERMEABILITY

Abstract

SUMMARYHigh-resistance micro-electrodes were used to measure membrane potentials in f-cells from islets of Langerhans of ob/ob obese mice (Norwich colony). In

Disorganization of cytoplasmic Ca 2+ oscillations and pulsatile insulin secretion in islets from ob / ob mice

“…[44]. Recordings with intracellular electrodes have shown that glucose induces oscillations of the membrane potential with bursts of action potentials in ob/ob beta cells within intact islets, but have identified several differences with the electrical pattern in normal mouse islets [45]. However, the authors emphasised that their observations, made with ob/ob mice from the Aston colony, might not be applicable to ob/ob mice of the Umea colony.…”

Differential effects of the K+ channel blockers apamin and quinine on glucose‐induced electrical activity in pancreatic β‐cells from a strain of ob/ob (obese) mice

“…Indeed, exposure to apamin depolarized the ob/ob @cell membrane as is the case for quinine in islets from normal mouse [2] and, furthermore, the toxin impaired the hyperpolarizing effect of CCCP. This uncoupler of oxidative phosphorylation has been reported to hyperpolarize the P-cell membrane through activation of Px-Ca, leading to cessation of spike activity, both in islets from albino mice [14] and from ob/ob mice [9]. In addition, apamin affected the spike characteristics.…”

“…As in other ob/ob P-cells, bursts of variable duration were recorded (see [9]). Addition of 4 nM apamin slightly increased the spike amplitude, whilst exposing the same islet to 40 nM apamin clearly increased the time spent in the active phase.…”

“…In islets of Langerhans isolated from both Wistar rats and albino mice, Px-Ca has been shown to be blocked by quinine [2] and resistant to apamin [4], a bee venom neurotoxin which has been reported to block Px-Ca in other cell types ( [5-g], review [16]). Recently, pancreatic islets from ob/ob mice (Norwich colony) were shown to exhibit a modified pattern of electrical response to glucose and to be poorly sensitive to quinine [9]. In an attempt to further characterize the properties of Pk-Ca in the ob/ob P-cell, the effects of apamin and quinine on glucose-induced electrical activity were compared in islets from the same strain of ob/ob mice.…”

“…In an attempt to further characterize the properties of Pk-Ca in the ob/ob P-cell, the effects of apamin and quinine on glucose-induced electrical activity were compared in islets from the same strain of ob/ob mice. as an out-bred colony in the animal house of the School of Biological Sciences, University of East Anglia (Norwich, England) [9] were used in this study. The ob/ob islets had an average diameter 4-5-times the regular size of islets from albino mice (from now on referred to as normal mice).…”