mu-Opioid influence on transmesothelial resistance of isolated sheep pleura and parietal pericardium.

The effect of morphine (mu-opioid receptor agonist) on the transmesothelial resistance (R(TM)) of sheep's pleura and parietal pericardium was studied using the Ussing chamber technique. Basal transmesothelial resistance of parietal pleura was found to be 19.57+/-0.32 Omega cm2 and of visceral pleura was found to be 19.41+/-0.31 Omega cm2, whereas that of parietal pericardium was found to be 22.83+/-0.4 Omega cm2. Immediately after the addition of morphine (10(-9) M) both apically and basolaterally on the parietal pleura and parietal pericardium, these values were significantly increased (P<0.05). On the contrary, addition of morphine (10(-9) M) resulted in a rapid increase, only when placed basolaterally on the visceral pleura (P<0.05). In conclusion, our findings suggest that morphine, probably through mu-opioid stimulation, increases in vitro the transmesothelial resistance of the parietal pleura, of the visceral pleura when added basolaterally and of the parietal pericardium.