Cosmos 1887 mission overview: effects of microgravity on rat body and adrenal weights and plasma constituents.

The Cosmos 1887 biosatellite carried 10 male rats and 2 rhesus monkeys on its 12.5-day mission. Upon re-entry the Vostok vehicle overshot the designated landing site, which resulted in fasting of the animals for 42 h, exposure to cage temperatures of 12-15 degrees C, and 2 days delay in death of the rats. No overt untoward effects of the delayed recovery were apparent. Tissues from the rats were harvested by Soviet scientists, appropriately preserved, and provided to U.S. investigators. Flight rats grew more slowly and had larger adrenal glands than earth gravity controls. Analysis of plasma revealed increased concentrations of hepatic alkaline phosphatase, glucose, urea nitrogen, and creatinine in flight rats. In contrast, electrolytes, total protein, albumin, corticosterone, prolactin, and immunoreactive growth hormone levels were unchanged. However, testosterone concentration was marginally decreased after flight and thyroid hormone levels were suggestive of reduced thyroid function. Due to the possible effects of reentry and the delay in recovery of the animals, it is not clear what relationship postflight levels of plasma constituents bear to their concentrations in flight.