Folinic acid protection against hematopoietic depression induced by nitrous oxide in rats.

We studied the degree of hematopoietic depression and spontaneous recovery of depressed hematopoietic cells with 50% nitrous oxide-oxygen inhalation for 6 or 12 h in 120 Sprague-Dawley rats. Bone marrow and blood were sampled serially immediately after, 1 day, 3 days, and 1 wk following nitrous oxide inhalation. After 1 wk of culturing of hematopoietic stem cells, the number of the colony-forming units of granulocytes and monocytes and the colony-forming units of T lymphocytes grown from bone marrow and blood were counted. There was no change in the number of colonies immediately after inhalation compared with the control group, but there was a significant decrease in the number of colonies 1 and 3 days after inhalation (P<0.001), and 1 wk after inhalation, there was spontaneous recovery without any treatment