Clinical and experimental investigations of vasopressin secretion in acute porphyrias.

In 41 patients suffering from acute hepatic porphyrias the arginin-vasopressin (AVP) levels in their urine were measured by RIA. In 6 patients, AVP secretion was normal; in 8 cases AVP levels were significantly elevated, while 27 cases showed decreased levels of AVP (p less than 0.001). A linear correlation between AVP secretion and urine volume was not found. In animal experiments, 20 rats were treated with delta-aminolevulinic acid (ALA), (1.5 mmol/kg/24 h and 1.5 mmol/kg/48 h) for 4 weeks. Afterwards vasopressin production in the hypothalamo-hypophyseal system was analysed by the immunoperoxidase technique and a microdensitometric method. In ALA-treated animals, AVP positive neurones showed coarse-grained granules of different intensity and a distinct increase of peroxidase positive granules in the zona interna of the eminentia mediana. Furthermore, in comparison with the control group in ALA-treated animals the mean diameter of nuclei in AVP positive neurons was greater. While animals treated daily showed an increase of transmission in the pituitary, microdensitometric findings in animals treated at 48 hourly intervals showed an equal transmission in AVP producing nuclei compared to the control group. Our results seem to point to a toxic effect of porphyrin precursors on the CNS, which may also induce via hypothalamus lesion either diabetes insipidus or a SIADH-syndrome.