Calcium contraction sensitivity modulation

The concept that the Ca +-sensitivity of contraction could be modulated was developed when it was shown that cAMP relaxed skinned smooth muscle strips at constant submaximal [Ca +] and shifted the calcium force relation to the right towards higher values (cf. Riiegg 1992). It has also been shown that excitatory agonists that activate heterotrimeric G-proteins can increase LC20 phosphorylation and force at constant [Ca ] (Somlyo and Somlyo 1994). In this context, a decrease in Ca -sensitivity refers to a shift in the relation between [Ca +] and phosphorylation or force towards higher [Ca +] an increase in Ca +-sensitivity is a shift towards lower [Ca " ]. The physiological relevance of the Ca +-sensitivity modulation became apparent when simultaneous measurements of intracellular [Ca +] and force in intact smooth muscle showed that there was no unique rela-... 

Pozzan T, Rizzuto R, Volpe P, Meldolesi J (1994) Molecular and cellular physiology of intracellular calcium stores. Physiol Rev 74 595-636 Raeymakers L, Wuytack F (1996) Calcium pumps. In Barany M (ed) Biochemistry of smooth muscle contraction. Academic Press, San Diego, pp 241-253 Rembold CM (1990) Modulation of the [Ca " ] sensitivity of myosin phosphorylation in intact swine arterial smooth muscle. J Physiol 429 77-94 Rembold CM, Weaver BA (1990) [Ca ], not diacylglycerol, is the primary regulator of sustained swine arterial smooth muscle contraction. Hypertension 15 692-698 Shimada T, Somlyo AP (1992) Modulation of voltage-dependent Ca channel current by arachidonic acid and other long-chain fatty acids in rabbit intestinal smooth muscle. J Gen Physiol 100 27-44... 

---