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Circulating immunoreactive intact human parathyroid hormone (PTH) was measured by a direct immunoradiometric assay (IRMA) and the results compared with a radio-immunoassay (RIA) which required extraction and concentration prior to assay. The sensitivity of the IRMA was better than that of the RIA (0.6 vs 2.0 pmol/L). In control subjects the hPTH concentrations ranged between 0.6 and 6.7 pmol/L and in patients with hypercalcaemia due to malignant diseases, sarcoidosis and hypoparathyroidism none could be detected. In patients with primary hyperparathyroidism the concentrations ranged from 5.2 to 27.0 pmol/L. In patients with renal osteodystrophy serum human PTH concentrations ranged from 7.6 to 285 and in those with chronic renal failure but without evidence of renal osteodystrophy from 0.5 to 5.2 pmol/L. The major advantages of the IRMA are its much simpler performance and its higher sensitivity which makes studies of the physiology of PTH secretion in humans possible.

The endocrine regulation of molting was investigated in the crab Gecarcinus lateralis by treating tissues from anecdysial (intermolt) animals with the arthropod molting hormone 20-hydroxyecdysone (20HE) in vitro and observing changes in the incorporation of [35S]-methionine into proteins. Although total protein synthesis was not affected by levels of 20HE ranging from lo-' to lop5 M, synthesis of five out of 30 protein bands was significantly stimulated at hormone concentrations of 10-9-10-7 M, the latter characteristic of proecdysis. Increases were as large as eightfold. Synthesis was not significantly inhibited for any of the integumentary proteins. Treatment of integumentary tissues with M 20HE (approx. 100 times greater than the highest endogenous concentration) had less effect than physiological concentrations. The dose response varied substantially among integumentary proteins. In some instances, the effects were similar to changes in synthesis that occur in vivo during specific stages of proecdysis (Stringfellow and Skinner, Dev. Biol., 128:97-110, ' 881. Midgut gland (hepatopancreas) was also treated with 20HE in vitro. Treatment with 20HE significantly inhibited total protein synthesis in tissue from males, but not in that from females. This treatment inhibited the synthesis of a number of the 32 protein bands examined in both sexes. Synthesis of six protein bands was significantly inhibited in males, while synthesis of three different bands was significantly inhibited in females. This inhibitory action of 20HE is consistent with the atrophy of the midgut gland that occurs during proecdysis (Gibson and Barker, Oceanogr. Mar. Biol. Annu. Rev., 17:285-346, '79).

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