The submandibular gland of the mouse contains a variety of hormone-like proteins and enzymes, such as epidermal growth factor (EGF), nerve growth factor (NGF), and submandibular gland renin-like enzymes (SGR). Dispersed cells from the submandibular gland of male mice were prepared by treatment with collagenase to study the mechanisms by which these specific proteins are secreted in vitro. All three proteins were secreted concomitantly in vitro by the dispersed submandibular gland cells. Norepinephrine, epinephrine, and phenylephrine, all α-adrenergic agonists, stimulated release of these three proteins in a dose-dependent manner, whereas isoproterenol, a β-adrenergic agonist, and carbamylcholine, a cholinergic agonist, did not. The effect of α-adrenergic agonists was inhibited either by removal of calcium ions from the incubation medium or by the addition of verapamil, a selective blocker of extracellular calcium influx. The divalent cation ionophore, A-23187, stimulated release of all three proteins in a dose-dependent manner only in the presence of calcium ion, but not in the presence of magnesium ion. Thus, the ionophore mimicked the action of α-adrenergic agonists. Dibutyryl cAMP, dibutyryl cGMP, methylisobutylxanthine, and a variety of hormones or other biologically active peptides found in the alimentary tract, brain, and/or skin had no effect on the release of EGF, NGF, or SGR. The apparent molecular sizes of all three proteins secreted into the medium were similar to those found in mouse saliva; that is, they were similar to those of the respective highly purified standard. However, submandibular gland extract contained high molecular weight EGF and NGF components which dissociated under conditions of extreme pH to yield standard small molecular weight EGF and NGF, respectively. The secretion of EGF, NGF, and SGR appears to be similarly initiated by activation of α-adrenergic receptors and apparently involves a mechanism independent of cyclic nucleotides but dependent upon influx of extracellular calcium ion.
YASUJIMA, M., KANAZAWA, M., YOSHIDA, K., KOHZUKI, M., WATANABE, H., HIWATARI, M., SATO, T., ABE, K., HIRATA, Y. and YOSHINAGA, K. Chronic Treatment with Anti-Endothelin Antibodies Fails to Modify the Development of Hypertension in Stroke-Prone Spontaneously Hypertensive Rats and DOCA-Salt Hypertensive Rats. Tohoku J. Exp. Med., 1993, 169 (1), 43-50-This study was designed to assess whether blocking endogenous endothelin with anti- endothelin antibodies could alter the development of hypertension in stroke-prone spontaneously hypertensive rats (SHR) and DOCA-salt treated rats. Specific anti-endothelin antibodies were produced in rabbits by standard methods. The amount of anti-endothelin antibodies employed in this study blocked the hypertensive effect of endothelin-1, 750ng/kg, by 55% in conscious rats. Intravenous injection of anti-endothelin antibodies as a bolus twice a week for 3 weeks did not affect the rise in blood pressure of stroke-prone SHR (268±8mmHg, n=8) compared to control stroke-prone SHR (256±7mmHg, n=8) treated with normal rabbit serum. Intravenous administration of anti-endothelin antibodies in a same manner also failed to alter the development of hypertension in DOCA-salt treated rats (160±6mmHg in anti-endothelin antibodies-treated group, n=7 compared to 164±5mmHg in normal rabbit serum-treated group, n=7). The administration of anti-endothelin antibodies did not induce any significant changes in body weight, urine volume and urinary sodium excretion in stroke-prone SHR and DOCA-salt treated rats compared to those treated with normal rabbit serum. These findings suggest that circulating endothelin might not play a major role in the regulation of blood pressure in stroke-prone SHR and DOCA-salt treated rats. -endothelin; anti-endothelin antibodies; stroke-prone SHR; DOCA-salt hypertensive rats; hypertension
There are two main subtypes of GH-producing pituitary adenoma: densely granulated (DG-type) and sparsely granulated (SG-type). Despite the difference in drug responsiveness between the two subtypes, their molecular mechanisms remain unknown. The aim of this study is to evaluate the differential expression of genes related to drug responsiveness between the two subtypes of somatotroph adenoma, and their relationship to the clinical characteristics. Eighty-two acromegaly patients (44 DG-type, 38 SG-type) were studied retrospectively. Clinical characteristics were compared between the two subtypes. Among them, 36 tumor tissue specimens (19 DG-type, 17 SG-type) were available for investigation of the expression of SSTR2, SSTR5 and D2R that are reported to be involved in drug responsiveness by realtime RT-PCR. Protein level was evaluated by immunohistochemical study. Patients with SG-type adenomas were younger in age and showed greater GH suppression by octreotide, but not by bromocriptin, and bigger in size and more invasiveness than DG-type adenomas. The mRNA expression of SSTR2 in DG-type adenomas were greater than those in SG-type adenomas and showed significantly positive correlation with GH suppression by octreotide. There was positive correlation between mRNA and protein levels of SSTR2. These data suggested that the differences of responsiveness to octreotide between DG- and SG-type adenomas are based on the expression levels of SSTR2.
