Force relaxes before the fall of cytosolic calcium in the photomechanical response of rat sphincter pupillae
| Autor: | Lloyd Barr, Andrew P. Krivoshik |
|---|---|
| Rok vydání: | 2000 |
| Předmět: |
Agonist
medicine.medical_specialty Light Physiology G protein medicine.drug_class chemistry.chemical_element Calcium Biology Rats Sprague-Dawley chemistry.chemical_compound Cytosol Internal medicine medicine Animals Receptor Phospholipase C Osmolar Concentration Muscle Smooth Pupil Inositol trisphosphate Cell Biology Rats Endocrinology chemistry Biophysics medicine.symptom Signal transduction Photic Stimulation Muscle Contraction Muscle contraction |
| Zdroj: | American Journal of Physiology-Cell Physiology. 279:C274-C280 |
| ISSN: | 1522-1563 0363-6143 |
| DOI: | 10.1152/ajpcell.2000.279.1.c274 |
| Popis: | In the rat sphincter pupillae, as in other smooth muscles, the primary signal transduction cascade for agonist activation is receptor → G protein → phospholipase C → inositol trisphosphate → intracellular Ca2+concentration ([Ca2+]i) → calmodulin → myosin light chain kinase → phosphorylated myosin → force development. Light stimulation of isolated sphincters pupillae can be very precisely controlled, and precise reproducible photomechanical responses (PMRs) result. This precision makes the PMR ideal for testing models of regulation of smooth muscle myosin phosphorylation. We measured force and [Ca2+]iconcurrently in sphincter pupillae following stimulation by light flashes of varying duration and intensity. We sampled at unusually short (0.01–0.02 s) intervals to adequately test a PMR model based on the myosin phosphorylation cascade. We found, surprisingly, contrary to the behavior of intestinal muscle and predictions of the phosphorylation model, that during PMRs force begins to decay while [Ca2+]iis still rising. We conclude that control of contraction in the sphincter pupillae probably involves an inhibitory process as well as activation by [Ca2+]i. |
| Databáze: | OpenAIRE |
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