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医学部小児科学教室 大澤眞木子教授退任記念特別号

A 43-year-old man, who had been treated for chronic schizophrenia, was admitted to our hospital with the chief complaint of urinary retention. His serum levels of sodium and osmotic value were low and serum creatine phosphokinase (CPK) was elevated to 2, 624 mg/dl. He had been consuming about 9 liters of water a day for ten years. A diagnosis of water intoxication was made and treated successfully with water restriction and drip infusion. To our knowledge, this is the 23rd case of water intoxication with serum creatine phosphokinase elevation reported in the Japanese literature and this is the first case with the chief complaint of urinary retention.

A 27-year-old woman with schizophrenia disorder developed water intoxica- tion due to primary polydipsia in drug-free state. Manner of vasopressin secretion was investigated with water loading and hypertonic saline infusion. The sensitivity of vasopres- sin secretion response to changing osmolality was low in this patient, which might be involved in the occurrence of water intoxication, linked to Type Ⅳ SIADH.

We designed this study to elucidate the manner of arginine-vasopressin (AVP) secretion in non-medicated schizophrenic patients. Plasma AVP level and osmolality (OSM) were measured before and after oral water loading in 14 normal volunteers, 20 non-medicated and 27 medicated schizophrenic patients with psychotropic drugs. Water loading test was performed twice, before and during medication, in the same 13 schizophrenic patients. 1. Simple regression analysis did not show significant differences in AVP secretion manner between the control and non-medicated groups. The sensitivity of AVP secretion response to osmolality in the medicated group was lower than that in the normal control group, suggesting that the psychotropic drug was a major factor in the change of AVP secretion manner. 2. In the medicated patients the basal levels of plasma AVP and ΔAVP/ΔOSM were lower than those in the same and non-medicated patients. 3. Multiple regression analysis in the non-medicated patients revealed associations of the Brief Psychiatric Rating Scale scores to their basal levels of AVP. AVP levels were related positively to acute symptoms and negatively to conceptual disorders in the patients.

The present study was designed to elucidate the manner of atrial natriuretic peptide (ANP) and vasopressin (AVP) secretion, which involves the development of water intoxication in patients with chronic psychosis. Plasma ANP level and plasma AVP level to plasma osmolality were measured before and after oral water loading in fifteen psychotic patients and in fifteen normal controls. 1) In the patient group, plasma AVP was detected even below 270 mOsm/kg. Sensitivity of AVP secretion to osmolality was lower in the patient group than in the control group. 2) The level of ANP was higher in the patient group than in the control group before and after water loading. There was a negative exponential correlation between ANP level and plasma osmolality in the patient group. 3) From these results, we infer that water intoxication in schizophrenic patients might be 'hypovasopressinemic antidiuresis' (one type of SIADH), linked with ANP secretion.

The present study was designed to elucidate the mechanism of water intoxication, which occurs almost exclusively in patients with chronic psychosis. 1) Animal experiments : Twelve rabbits were given neuroleptics for eight weeks. From measurement of arginine-vasopressin (AVP) secretion response to varied osmotic stimuli, it was suggested that chronic neuroleptics administration might raise the sensitivity of AVP secretion response. 2) Clinical study : In seventeen chronic schizophrenic patients with hyponatremia and sixteen chronic schizophrenic patients without hyponatremia, the manner of AVP secretion was investigated. In both the schizophrenic groups plasma AVP was secreted even below 270 mOsm/kg osmolality. Sensitivity of AVP secretion response to osmolality was decreased in schizophrenic patients, regardless of the presence of hyponatremia. 3) From these results, it is postulated that primary low sensitivity of osmoreceptor and secondary renal hypersensitivity to AVP could cause "hypovasopressinemic antidiuresis (SIADH)", further linked with the occurrence of water intoxication in schizophrenic patients.