Effect of ovarian hormones, pregnancy and lactation on somatostatin and substance P in the alimentary tract of mice.

Immunoreactive somatostatin and substance P were determined in extracts of alimentary tract (stomach to colon) from the following groups of adult female mice: intact control, ovariectomized, ovariectomized and treated with oestradiol (50 micrograms/kg per day) and/or progesterone (2 mg/kg per day) for 30 days, 19-day-pregnant, and 10-day-postpartum lactating. Ovariectomy increased the somatostatin concentration of the stomach (by 52%, P less than 0.05), jejunum (by 116%, P less than 0.01) and caecum (by 114%, P less than 0.01). These effects were partially or totally prevented by the oestradiol and progesterone treatments, especially the oestradiol-progesterone combination, except for an increase (by 126%, P less than 0.01) in gastric somatostatin after treatment with oestradiol alone. Lactation also increased gastric somatostatin (by 108%, P less than 0.001), but the somatostatin concentration of other regions of the alimentary tract (jejunum to colon) was reduced (by 21-55%, P less than 0.05) in pregnant and lactating mice. The concentration of substance P was increased by ovariectomy in stomach (by 69%, P less than 0.01), duodenum (by 84%, P less than 0.05), ileum (by 163%, P less than 0.001) and caecum (by 57%, P less than 0.01). This effect was partially or totally prevented by treatment with progesterone alone and by the oestradiol-progesterone combination, but not by oestradiol alone. Pregnancy and lactation increased gastric substance P by 46% (P less than 0.01) and 61% (P less than 0.001) respectively, but substance P concentrations in other regions of the alimentary tract were not significantly altered.(ABSTRACT TRUNCATED AT 250 WORDS)