Calcium dependency of massive postmortem bronchoconstriction in guinea pig lungs

Calcium antagonists were employed to examine whether or not guinea pig's postmortem bronchoconstriction is calcium dependent. First, a group of 17 young (3-4-week-old) animals were divided in three subgroups: control, nifedipine, and 8-(N,N-diethylamino)-octyl-3,4,5-trimethoxybenzoate (TMB-8, an intracellular calcium antagonist). A second group of 12 mature (5-7-week-old) animals were divided into two subgroups: control and nifedipine. Baseline pressure-volume (P-V) curves were performed prior to cannulation of the pulmonary artery in the anesthetized, opened chested animal. The lungs of the animal were then perfused and P-V curves were obtained again at intervals for up to 60 min. Nifedipine (10(-6) M) or TMB-8 (5 X 10(-4) M) was added to the perfusate in experimental groups. A temporal decrease in inflation volume (IV, the lung volume between transpulmonary pressure of 0 and 30 cm H2O during inflation) was used as an indicator of bronchoconstriction. In control subgroups, the decrease in IV was significantly greater (P less than 0.05) in the young (29.5 +/- 12.9% baseline at 20 min) than in the mature animals (75.0 +/- 7.0% baseline at 20 min). Nifedipine significantly alleviated (P less than 0.05) the decrease in IV in young animals at 15-30 min (58.6 +/- 8.4% baseline at 20 min) while TMB-8 (90.6 +/- 2.1% baseline at 20 min) prevented the decrease even further. Nifedipine did not have a significant effect on IV in mature animals. These data suggest that the postmortem bronchospasm is much more severe in young animals and that this severe constriction is calcium dependent.