The effects of temperature on contractile mechanisms of rainbow trout (Salmo gairdneri) intestine

Abstract

Experiments were designed to determine whether contractility of trout smooth muscle in vitro varied with temperature and if changes occurred at the receptor or intracellular levels. The role of calcium in contractility at various temperatures was also investigated. Isolated trout intestinal segments, approximately 2 cm in length, were suspended isometrically under 2 g tension in 10-mL organ baths containing trout Ringer's solution aerated with O2 and CO2 (95:5). Contractions of trout intestine were not statistically different at 10 and 20 degrees C for carbachol, 5-hydroxytryptamine, and KCl. However, the efficacy, but not the potency, of each agonist was decreased at 2 degrees C. Receptor-induced contractions were reduced to a greater extent at 2 degrees C and did not recover to the same extent when returned to 10 degrees C in comparison with those induced by depolarization. The calcium source for contractility was also dependent on temperature. As temperatures increased, utilization of intracellular calcium increased, as indicated by increased contractility in the absence of extracellular calcium. Thus, low temperatures decrease smooth muscle contractility by affecting receptor-mediated events rather than the intracellular contractile mechanisms. Receptor-operated agonists appear to have a higher capability of using intracellular calcium than depolarizing agents.

The effects of acute temperature change on smooth muscle contractility of rainbow trout (Oncorhynchus mykiss Walbaum) intestine

“…The effects of temperature are likely directed at the enzymatic mechanisms involved in smooth muscle contraction since most metabolic processes are temperature dependent over a specific range (Sizer 1943;Prosser 1991). However, receptor properties of smooth muscle, including the function of voltage-operated calcium channels, can be affected by temperature changes (Cook et al 1977;Wolowyk et al 1987;Burka et al 1990). Changes in receptors in rainbow trout intestinal smooth muscle appear to occur when a rapid temperature change is applied to tissue in vitro (Burka et al 1990).…”

“…However, receptor properties of smooth muscle, including the function of voltage-operated calcium channels, can be affected by temperature changes (Cook et al 1977;Wolowyk et al 1987;Burka et al 1990). Changes in receptors in rainbow trout intestinal smooth muscle appear to occur when a rapid temperature change is applied to tissue in vitro (Burka et al 1990). Some of these effects can also be attributed to intracellular contractile mechanisms (Burka et al 1990).…”

“…Changes in receptors in rainbow trout intestinal smooth muscle appear to occur when a rapid temperature change is applied to tissue in vitro (Burka et al 1990). Some of these effects can also be attributed to intracellular contractile mechanisms (Burka et al 1990). If sudden temperature changes are imposed on live fish, then changes in smooth muscle physiology could be influenced by other adaptive mechanisms, such as hormonal modifications, occuring in the organism.…”

“…We had previously noted that contractility of trout intestine in vitro is temperature-dependent (Burka et al 1990). In that study, segments of intestine from trout acclimated to 10 0 C were subjected to altered temperatures of the physiological solution in isolated organ baths.…”

Changes in smooth muscle contractility of rainbow trout (Oncorhynchus mykiss Walbaum) intestine during acclimation to altered temperature

“…The cited studies utilized fish which had been temperature acclimated (4-20°C) for 6 to 8 weeks prior to experimentation. The contractility of rainbow trout gastrointestinal smooth muscle in vitro also depends on temperature (Burka et al 1990(Burka et al , 1993. Those studies showed a marked linear increase in efficacy and a slight increase in potency to the smooth muscle contractile agonists, 5-hydroxytryptamine (5-HT; serotonin) and carbachol, the depolarizing agent, KCI, and transmural electrical stimulation (TMS) of the muscle with increasing temperature.…”