Airline pilots divided into two groups of age (over and under 50 years) were studied before, during and after westbound (Madrid-Mexico City-Madrid, n = 12) and eastbound (Madrid-Tokyo-Madrid, n = 21) flights. A group of 10 age-matched people staying in Madrid were submitted to the same tests and served as a control group. Changes in urinary 6-sulphatoxymelatonin (6-aMTs) and free cortisol excretion (determined in 6-hr intervals) were measured by radioimmunoassay. Using wrist actigraphy, the circadian locomotor activity rhythm (LAR) was also monitored. Maximal baseline excretion of 6-aMTs occurred between 00:00 and 12:00 hr and maximal excretion of cortisol took place between 6:00 and 12:00 hr in the control group. Analysed globally, older pilots exhibited significantly lower values of 6-aMTs than younger ones. In both flight directions, pilots maintained the pattern of excretion of 6-aMTs, corresponding to baseline. The return flight to Madrid from Mexico and Tokyo coincided with a maximum in 6-aMTs excretion. Pilots kept the cortisol pattern found in the control group, with those over 50 years of age exhibiting significantly lower cortisol values than the younger ones. A 7-hr delay in acrophase of LAR after 2 days in Mexico City was found after cosinor analysis, and similar pre-flight values were found after returning to Madrid. An 8-9-hr acrophase advance of LAR was observed after arriving in Tokyo, with acrophase on the post-return flight day still being advanced 3 4 hr as compared to pre-flight values. Decreases in the amplitude of LAR in older pilots were found at Mexico City, as well as at Tokyo stopover and on post-flight day. Data confirm the occurrence of internal desynchronization in airline crewmembers after transmeridian flights.

Twelve female rats weighing 150 g received in the submaxillary gland a pellet capable of releasing 3·5 µg GHRH/h for 60 days. Another eight sex-and weightmatched animals received placebo pellets in the same place. After two months the animals were killed, heart blood was collected and pituitary and submaxillary glands were carefully dissected. Pituitary GH content in both placebo-and GHRH-treated animals showed similar values, but plasma GH and IGF-I levels were significantly lower in the animals carrying GHRH pellets (P<0·03); these animals also had a significantly higher GH content in the submaxillary gland (19·2 8 ng/mg protein) compared with the placebo-treated group (1·1 0·3 ng/mg protein). GH mRNA was present only in the submaxillary gland of GHRH-treated rats as determined by PCRSouthern blot and by in situ hybridization methods. It is concluded that high local GHRH levels are capable of inducing transdifferentiation in submaxillary gland cells to synthesize GH.

To test whether salivary tissue can secrete pituitary hormones, female Sprague-Dawley rats were hypophysectomized (hypox) and the following were transplanted to the sella turcica: parotid gland (group 3, n=33), adrenal gland (group 4, n=30), muscle (group 5, n=24). Group 2 (n=21) had the sella turcica filled with dentist's cement. In addition a group of rats (group 1, n=22) remained intact as controls. All groups were followed for 8 months. Daily vaginal smears showed normal cyclicity in controls and constant dioestrus in all hypox groups. Blood samples, taken once every 30 days before and after LHRH stimulation, showed significantly lower (P<0·001) plasma LH values in all hypox groups compared with controls. In group 3, a gradual and significant increase (P<0·05) was observed in the LH response to LHRH in parallel with a partial recovery of oestrous smears. No LH modification was observed in the other hypox groups. Plasma prolactin (PRL) levels were also very low in all hypox groups and were unaltered throughout the study. At the end of the experiments, half the animals were killed by decapitation and the hypothalamic-pituitary areas carefully dissected, homogenized and analysed for LH and PRL content. The remaining animals were perfused with 4% paraformaldehyde to obtain fixing of the whole body tissues. Hypothalamic and transplant areas were carefully dissected, frozen, cut and submitted to immunochemical procedures. LH content in the graft of group 3 animals was markedly (P<0·001) lower than in the control pituitary, but significantly higher (P<0·05) than in the other hypox groups. Immunochemistry showed LH and PRL positive cells in the graft of group 3 animals, whereas neither positive cells, nor LH content were observed in the parotid gland in situ. Experiments were completed with in vitro cultures of parotid glands in the presence or absence (controls) of synthetic hypothalamic hormones or rat hypothalamic extracts. After 1·5 weeks of culture, a significantly higher LH concentration (P<0·05) was observed in the wells treated with synthetic hypothalamic hormones (216 46 pg/ml vs 41 6 pg/ml in controls). When hypothalamic extracts were used, the LH levels increased more markedly (1834 190 pg/ml vs 36 6 pg/ml in controls) and those values were maintained during 3 weeks of culture. Immunostaining of these cultures showed a positive LH reaction in the epithelial cells found in the hypothalamic extract-treated wells. Both in vivo and in vitro studies confirm the transdifferentiation of parotid gland tissue to pituitary hormone-producing cells under hypothalamic influence.

The pattern of long-term GHRH administration capable of stimulating GH release without depleting pituitary GH content has been investigated using two experimental approaches. In experiment 1, recently weaned male lambs were treated for 3 weeks as follows: Group A) control; B) subcutaneous (sc) continuous infusion of GHRH (1200 mg/day) using a slow release pellet; C) the same as B plus 1 daily sc injection of long acting somatostatin (SS) (octreotide, 20 mg) ; D) 3 daily sc GHRH (250 mg) injections ; E) 2 daily sc injections of GHRH (250 mg) and 2 of natural SS (250 mg). In experiment 2, recently weaned male lambs were continuously GHRH-treated using sc osmotic minipumps (900 mg/day) alone or combined with a daily sc injection of octreotide (20 mg) for 4 weeks. Basal plasma GH levels were increased after chronic pulsatile GHRH treatment but not after any kind of continuous GHRH administration. This increment was maintained during the 3 weeks of experimentation and appeared accompanied by a pituitary GH content similar to controls. A marked GH response to the iv GHRH challenge was observed in controls and in lambs receiving both types of continuous sc GHRH infusions, whereas pulsatile sc GHRH-treated animals did not respond to the iv GHRH challenge in the first and second weeks of the study but did so in the third week of treatment. These data demonstrate that long-term pulsatile GHRH administration is capable of stimulating GH release in growing male lambs, without producing pituitary desensitization.