Calcium absorption in the rat as influenced by highly selective vagotomy with special regard to endogenous gastrin

The effect of HSV (controls: sham), which induces hypergastrinemia, on duodenal Ca absorption was studied in "intact", TPTX, PTX, and TX rats. Ca absorption was estimated by an in vivo loop technique. As this technique increased serum gastrin by the duodenal Ca load, gastrin was also measured in rats not subjected to evaluation of Ca absorption. Following vagotomy gastrin rose significantly in "intact" as well as in TPTX, PTX, and TX rats. Further, intraduodenal Ca increased gastrin both after sham and vagotomy. However, gastrin in vagotomized rats was significantly higher than in sham rats, too. Although duodenal Ca absorption was not altered by vagotomy in "intact" and in TX rats, it was significantly lowered in vagotomized TPTX and PTX rats. Pretreatment of TPTX rats by pentagastrin for 10 days or immediately preceding experiments did not change Ca absorption. In addition, serum parathyroid hormone was unchanged by vagotomy in "intact" rats as compared to sham controls. We conclude that (1) vagotomy does not influence the rate of duodenal Ca absorption in "intact" rats, (2) Ca absorption is lower after vagotomy only in the absence of parathyroid glands, and (3) this vagotomy effect is not mimicked by exogenous pentagastrin and therefore appears unrelated to endogenous postvagotomy gastrinemia.