Radioimmunoassay of vasopressin during pregnancy. Use and removal of cystylaminopeptidase inhibitors

This paper describes a radioimmunoassay (RIA) for arginine-vasopressin in which o-phenanthroline effectively inhibits cystyl-amino-peptidase activity in whole blood and plasma from pregnant women but in which o-phenanthroline is removed during the extraction of vasopressin from plasma to prevent disturbance of the RIA. Cystyl-amino-peptidase causes immediate degradation of vasopressin unless cystyl-amino-peptidase enzyme inhibitors such as o-phenanthroline are applied. However, o-phenanthroline interferes with RIA. We report an extraction procedure over octadecasyl silica-packed Sep-Pak C18 columns, by which cystyl-amino-peptidase as well as most of the cystyl-amino-peptidase inhibitor is removed from plasma with chloroform. The average o-phenanthroline concentration (0.25 mmol/l) found in the assay medium after extraction appeared not to interfere with the RIA. Polyacrylamide gel isoelectric focusing of extracts of platelet-rich and platelet-poor plasma from pregnant women revealed a single vasopressin immunoreactive peak in the RIA. Recovery and between-assay coefficients of variation of 3.2 ng/l vasopressin from pregnancy whole blood were comparable with non-pregnant controls (57%/8% and 59%/13%, respectively). Results with this assay compare well with those of another assay using inhibitors in pregnant subjects and with results in non-pregnant subjects.     

Prenatal development of the Brattleboro rat is influenced by genotype and lysine vasopressin treatment of the mother

Homozygous (Hom) Brattleboro rats suffer from severe diabetes insipidus (DI) as a consequence of the lack of arginine-vasopressin (AVP) in the brain. Compared with heterozygous (Het) AVP-synthesizing Brattleboro rats, Hom rats show disturbed body and brain development. In this study breeding experiments with Het and Hom rats were performed to determine whether prenatal conditions might contribute to the developmental disturbances in Hom pups. For this purpose Het and Hom females were mated with Hom and Het males, respectively. In addition lysine-vasopressin (LVP) was administered to half of the pregnant females, since this has previously been shown to stimulate birth weight of Hom pups. On day 1 postnatally the body and brain weight of Hom pups of nontreated Hom mothers was significantly smaller than that of the Het litter mates, whereas no difference was found between the weight of Het or Hom pups of nontreated or LVP-treated Het mothers. These results indicate an important role of the genotype of the mother in prenatal development of Hom pups. LVP administration failed to diminish the growth deficits, but increased protein and DNA content of the cerebellum of both Het and Hom pups. Notwithstanding the improved prenatal growth of Hom pups from Het mothers, postnatally retarded development was still observed: at 1 month of age there was a significant difference between the body, brain and cerebellar weight of Het and Hom pups from Het mothers. It was therefore concluded that the prenatal situation of the Hom mother, i.e. AVP-deficiency, significantly contributes to the developmental disturbance of the Hom pup, but also that growth impairment is linked to the presence of the mutation in the Hom pups themselves.     

The suprachiasmatic nucleus of the human brain in relation to sex, age and senile dementia

The suprachiasmatic nucleus (SCN) is considered to be the endogenous clock of the brain, essential for the ovulation cycle and the temporal organization of sleep-wake patterns, among other things. Immunocytochemical staining with anti-vasopressin as a marker permitted a morphometric study of this nucleus in the human brain, which revealed that the shape of the SCN is sexually dimorphic. The shape of the SCN was elongated in women and more spherical in men. In both sexes a decrease in SCN volume and cell number was observed in senescence (80-100 years). The latter change was especially pronounced in patients with senile dementia of the Alzheimer type (SDAT). This suggests the presence of a structural defect in the SCN which underlies the general disturbance of biological rhythms in senescence and SDAT.