Platelet morphology and membrane bound calcium in porcine stress syndrome.

Platelets of normal and stress susceptible pigs were subjected to electron microscopic examination and energy dispersive x-ray microanalysis in an attempt to study whether the cell membrane defect implicated in porcine stress syndrome is detectable at the platelet level. Electron microscopic studies revealed that the platelets of stress susceptible pigs are morphologically distinguishable from those of normal pigs by virtue of their highly dilated surface connected open canalicular system rendering the "Swiss cheese" appearance and the absence of the circumferential band of microtubules. A comparison of the data from spot analysis of cell membrane and the membranes of the open canalicular system using the energy dispersive microanalysis system showed that the calcium content of the plasma membrane of stress susceptible pigs is significantly lower than that of normal pigs. It would appear that the morphologic feature and the reduced levels of calcium bound to platelet membrane are related to the generalized membrane defect postulated to be the primary lesion in porcine stress syndrome and that these parameters could be included among the criteria for the detection of stress susceptible pigs.