Noriyuki Nihei

Serum triiodothyronine: measurements in human serum by radioimmunoassay with corroboration by gas-liquid chromatography

Serum triiodothyronine (T(3)) has been measured by radioimmunoassay and corroborated by analysis of the identical samples with a previously described gas-liquid chromatographic technique. Special features of the radioimmunoassay procedure which permit determinations in unextracted serum include the use of a T(3)-free serum preparation for the construction of the standard curve and of tetrachlorothyronine to inhibit binding of T(3) to thyroxine-binding globulin.T(3) values by radioimmunoassay were 138 +/-23 ng/100 ml (mean +/-SD) in 82 normal subjects, 62 +/-9 ng/100 ml in 45 hypothyroid patients, and 494 +/-265 ng/100 ml in 60 patients with toxic diffuse goiter. In the hypothyroid group, the range was similar in patients with both primary and secondary hypothyroidism. There was no overlap between the three thyroidal states. Elevated T(3) levels were seen in 40 cases that appeared clinically hyperthyroid but had normal serum thyroxine (T(3)) determinations, a syndrome we have called T(3) toxicosis. Values obtained with radioimmunoassay agreed closely with those we had previously found by gas-liquid chromatography which were 68 +/-2 ng/100 ml in hypothyroidism, 137 +/-23 ng/100 ml in normal subjects, and 510 +/-131 ng/100 ml in untreated toxic diffuse goiter. Since T(3) is very potent and its level varies in different clinical states, accurate T(3) measurements are required to assess a patients thyroid status properly. The radioimmunoassay for T(3) appears to be sufficiently sensitive, precise, and simple to permit its routine clinical application for this purpose.

High activity of cyclic 3',5'-nucleotide phosphodiesterase in sera of patient with phaeochromocytoma

Our previous observations that serum cyclic 3′,5′‐nucleotide phosphodiesterase activity varied in thyroid disorders and was positively correlated with thyroid function stimulated us to investigate the phosphodiesterase levels in sera of patients with pituitary and adrenal disorders, and the response to glucagon in normal subjects. Both serum cyclic AMP phosphodiesterase (cyclic AMP‐PDE) and cyclic GMP phosphodiesterase (cyclic GMP‐PDE) activities were measured at a low substrate concentration. Serum cyclic AMP‐PDE activity was elevated in five patients with phaeochromocytoma and was not elevated in patients with Cushings syndrome or acromegaly, compared to the level in normal subjects. Increased enzyme activities returned to normal after resection of the tumours. Intramuscular injection of glucagon to five healthy subjects elevated cyclic AMP levels and cyclic AMP‐PDE activity in plasma. These results imply that the increased cyclic AMP level by the activation of cyclase may have induced cyclic AMP‐PDE in the target organ and the soluble cyclic AMP‐PDE may leak into blood vessels from target organs.

Abnormal lymphocyte function precedes hyperglycaemia in mice treated with multiple low doses of streptozotocin.

SummaryTo investigate early immunological disturbances at the onset of diabetes, lymphocyte function and islet cell surface antibodies were studied in streptozotocin-treated C57BL/10 and B10.BR mice. In C57BL/10 mice, streptozotocin given in multiple low doses depressed lymphoblastic transformation to phytohaemagglutinin and pokeweed mitogen, but not to concanavalin A on day 6 after the first administration. On day 20, the transformation remained suppressed with phytohaemagglutinin, but recovered to the control level with pokeweed mitogen. In the early phase after treatment, the islet cell surface antibodies were elevated and then declined. Single high dose administration depressed responses to phytohaemagglutinin with no detectable islet cell surface antibodies. In B10.BR mice transformations to pokeweed mitogen and concanavalin A were suppressed in the early phase. The strain of mice may be a factor to be considered. Thus, it was suggested that the deterioration of immunological function with the formation of islet cell surface antibodies preceded the onset of hyperglycaemia in mice treated with multiple low doses of streptozotocin.

Studies on thyrotropin releasing hormone in cerebellar ataxia mutant mouse brain

The effects of cathecholamine on the regional TRH distribution in the brain was studied in rolling mouse Nagoya (RMN) and non-affected C3H mice. TRH was extracted from the hypothalamus, brain stem, cerebellum, and cerebrum one hour after i.p. injection of the precursor or inhibitors of cathecholamine. TRH was distributed throughout the brain of both affected and non-affected mice; however, in RMN, TRH levels were lower in the hypothalamus and higher in other areas. 1-Dopa caused a decrease of TRH in the brain stem but no change in other regions in the RMN brain, whereas it caused an increase in TRH levels in all areas of the C3H brain. Fusaric acid increased TRH in the hypothalamus of RMN and decreased it in the cerebellum; alpha-MPT also caused a decrease in the TRH level in the cerebellum. Reserpine increased the TRH level in the hypothalamus and decreased it in the cerebrum. From these results, it appears that cerebellar ataxia in RMN does not result from a decrease in the TRH, which is actually increased in the cerebellum. Catecholamine had different effects on TRH levels in RMN and the controls; this might be due to the excess accumulation of noradrenaline in the RMN brain.

The effect of various amines on TRH contents in rat brain

To study the effect of vatious amines on TRH contents in rat brain, various amines or inhibitor of synthesis of amines were injected into rat through i.v. or i.p.. Rats were decapitated and brain was frozen in dry ice and aceton. TRH contents in hypothalamus(H), cerebrum(C) and cerebellum and brain stem (C and S) were measured by TRH radioimmunoassay. TRH contents in normal rats were 3.9+/-0.5ng in H, 2.6+/-0.5NG IN C and 1.6+/-0.3ng in C and S. TRH contents in all parts of brain were increased in L-DOPA treated group and did not change in T3 or T4 treated group. TRH contents in all parts of brain were decreased in alpha-methyl-DOPA, alpha-methyl-para-tyrosine, fusaric acid and 5-HTP treated groups. In D,L-p-chlorophenylalanine treated group TRH contents in brain were increased only in hypothalamus. In L-DOPA or 5-HTP treated group with T4 or T3 preadministration, TRH contents in all parts of brain were same levels of L-DOPA or 5-HTP treated group. The above data suggested the TRH contents in rat brain were increased with increase of dopamine level in rat brain and decreased with increase of serotonine level or decrease of noradrenaline level in rat brain and inhibitory effect of T4 or T3 on TRH release might be mediated through dopaminergic and serotonergic mechanism.

Changes of Plasma Levels of TRH and Its Target Hormones by Two Hour Constant Intravenous Infusion of TRH Tartrate in Man

Constant iv infusion of TRH tartrate for 2 hours was administered to normal men in a dosage of 0.5 (n=4), 1.0 (n=2) and 2 (n=4) mg/120 minutes. Measurements at every 15 minutes were performed for plasma levels of TRH, TSH, Thyroxine (T4) and Triiodothyronine (T3) by radioimmunoassay. Plasma levels of TRH increased promptly and stayed at the same levels until the end of the infusion. The Mean Clearance Rate (MRC), Half-life and Volume of Distribution of TRH were respectively, 4.62 +/- 0.53 L/min. (M +/- SE), 17.8 +/- 3.8 minutes and 112 +/- 15 L in the 0.5 mg administered group and 6.38 +/- 2.50 L/min., 9.0 +/- 1.4 minutes and 82 +/- 30 L in the 2 mg administered group. Plasma levels of TRH increased in two phases, and increments of plasma TSH were dose dependable to the dosage of TRH. Plasma levels of T4 increased gradually in the course of TRH infusion and stayed at high levels even in the withdrawal phase of TRH. Plasma levels of T3 increased markedly during and after the TRH infusion in the 0.5 mg administered group, while increments of plasma T3 were minute in the 2 mg administered group. From the above data, it is suggested that the amount of TRH production in man, which is much more than has previously been reported, may indicate the existence of an extrahypothalamic synthesis of TRH in man.