Effect of urea and osmotic cell shrinkage on Ca2+ entry and contraction of vascular smooth muscle cells
Autor: | Carsten A. Wagner, Siegfried Waldegger, Gillian L. Busch, R. Fux, N. Orth, Helmut Heinle, Nubia Kristen Kaba, Günther Zempel, S. Wärntges, I. Lambert, Bernd Nilius, Fan Lang, Stephan M. Huber |
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Rok vydání: | 2000 |
Předmět: |
Osmosis
Vascular smooth muscle Physiology Clinical Biochemistry chemistry.chemical_element In Vitro Techniques Biology Calcium Muscle Smooth Vascular Calcium in biology chemistry.chemical_compound Physiology (medical) medicine Extracellular Animals Urea RNA Messenger Cells Cultured Voltage-dependent calcium channel Osmolar Concentration Electric Conductivity Intracellular Membranes Rats Biochemistry chemistry Vasoconstriction Biophysics Tonicity Calcium Channels Rabbits Mitogen-Activated Protein Kinases medicine.symptom |
Zdroj: | Pflügers Archiv - European Journal of Physiology. 440:295-301 |
ISSN: | 1432-2013 0031-6768 |
Popis: | The present study was performed to elucidate the effects of urea on vascular smooth muscle cells (SMC). Addition of urea (20, 50, 100 mM) to physiological salt solution blunted the vasoconstrictory effect of phenylephrine (by 17, 25 and 30%, respectively) and of an increased extracellular K+ concentration (by 7, 14 and 19%, respectively) without affecting the basal tone of rabbit arterial rings. According to Fura-2 fluorescence in cultured SMC (A7r5), urea had no effect on basal intracellular calcium activity ([Ca2+]i), but significantly blunted the increase of [Ca2+]i following an increase of extracellular K+. Whole-cell patch-clamp studies revealed that the Ca2+ current through voltage-sensitive Ca2+ channels is significantly inhibited in the presence of urea. As evident from calcein fluorescence, addition of urea leads to sustained cell shrinkage. The effects of urea on vascular tone, [Ca2+]i activity, voltage-gated Ca2+ channels and cell volume are mimicked by addition of raffinose or NaCl. However, the cell shrinkage induced by urea is sustained, whereas the addition of equiosmolar NaCl is only transient and followed by a regulatory cell volume increase. Moreover, hypertonic NaCl increases, whereas urea decreases, the transcription of cell-volume-regulated kinase hsgk. In conclusion, urea leads to sustained shrinkage of vascular smooth muscle cells, which is followed by inhibition of voltage-gated Ca2+ channels, a decrease of [Ca2+]i and thus blunts the vasoconstrictory action of phenylephrine and increased extracellular K+ concentration. |
Databáze: | OpenAIRE |
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