The mesangial cell culture: a tool for the study of the electrophysiological and pharmacological properties of the glomerular mesangial cell.
Cultured rat glomerular mesangial cells (MC) were evaluated as a tool for reliable electrophysiological measurements as well as for fluorimetric determinations of intracellular Ca++. They had a resting potential similar to that observed in cultured vascular smooth muscle cells (VSMCs), in VSMCs of mouse kidney arterioles, or in glomerular--presumably mesangial--cells of kidney slices. The comparison with the other cell types was carried out in order to look for features distinguishing them from these cells, e.g., active and passive electrical membrane properties or electrical membrane responses to vasoactive pharmacological agents. In MCs, as well as in the other cell types, the average membrane potential was approx. -50 mV. The vasoconstrictor peptides angiotensin II (ANG II) and arginine-vasopressin (AVP) caused depolarizations that could be blocked by the respective specific inhibitors of these compounds. The agonist-induced depolarizations have to be attributed, at least in part, to a Ca++ inward current. Norepinephrine, if any, had only a weak action upon MCs, whereas isoproterenol either did not influence the membrane potential or hyperpolarized the cells. Other substances tested, which had no influences upon the membrane potential, were neuropeptide Y and atriopeptin 3. As to their resting electrical properties and their responses to pharmacological agents, cultured mesangial cells did not differ from glomerular, i.e., most probably mesangial, cells in the kidney slice. The difference between mesangial cells and VSMCs consists in their reaction to noradrenaline. Whereas VSMCs respond with a marked depolarization, the noradrenaline effect upon MCs in culture and in the kidney slice is either absent or very weak. Repeated passage of the cells (more than six passages) led to a gradual loss of their responsiveness to the agonists, indicating reduced receptor expression which may be interpreted as dedifferentiation. This held for both cultured MCs and VSMCs. Fluorimetric measurements using the Ca++-specific indicators quin-2 and fura-2 were performed with a purpose-developed, ultrasensitive photon-counting microspectrofluorimeter. Individual MCs as well as isolated glomeruli responded to the vasoconstrictors ANG II and AVP with an increase in Ca++-dependent fluorescence indicating that these agents indeed depolarize the cells partly via a Ca++ influx and increase cytosolic free Ca++.(ABSTRACT TRUNCATED AT 400 WORDS)
Nobiling
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I. Physiologisches Institut der Ruprecht-Karls-Universität Heidelberg, FRG.
Bührle
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D000804:Angiotensin II / Q000494:pharmacology; D000818:Animals; D001127:Arginine Vasopressin / Q000494:pharmacology; D002118:Calcium / Q000378:metabolism / Q000502:physiology; D002455:Cell Division; D002478:Cells, Cultured; D046508:Culture Techniques / Q000379:methods*; D004594:Electrophysiology / Q000295:instrumentation* / Q000379:methods; D005456:Fluorescent Dyes; D007678:Kidney Glomerulus / Q000166:cytology* / Q000187:drug effects / Q000502:physiology; D008297:Male; D008564:Membrane Potentials / Q000187:drug effects; D008854:Microscopy, Electron; D009131:Muscle, Smooth, Vascular / Q000166:cytology / Q000502:physiology; D009638:Norepinephrine / Q000494:pharmacology; D051381:Rats; D011919:Rats, Inbred Strains
D005456:Fluorescent Dyes; D000804:Angiotensin II; D001127:Arginine Vasopressin; D002118:Calcium; D009638:Norepinephrine