Ten patients with debilitating hip or knee pain were examined with magnetic resonance (MR) imaging. All had conventional radiographs that were either normal or showed nonspecific osteopenia. Nine patients had bone scintigrams that showed focal increased radionuclide uptake in the region of the painful joint. In each case, MR images of the affected joint showed regional decreased signal intensity of the bone marrow on T1-weighted images and increased signal intensity on T2-weighted images. Biopsy results of four patients excluded ischemic necrosis and metastases. The symptoms resolved spontaneously in all cases. The ten patients were followed up for 12-36 months, and there were no recurrences. The authors believe that the findings on MR images represent a transient increase in bone marrow water content. The focal findings on scintigrams confirmed the periarticular distribution of the process and provided evidence of accompanying hyperemia and increased bone mineral metabolism. For lack of a better term and to emphasize the generic character of the condition, the authors termed this condition "the transient marrow edema syndrome."

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Responses to and the mechanism of action of adrenomedullin (ADM), the carboxy-terminal fragments of ADM, and calcitonin gene-related peptide (CGRP), a structurally related peptide, were investigated in the pulmonary vascular bed of the rat. Under conditions of elevated tone and controlled pulmonary blood flow in the isolated blood-perfused rat lung, injections of ADM, the 15-52 amino acid carboxy-terminal ADM analogue (ADM15-52), and CGRP caused dose-related decreases in pulmonary arterial perfusion pressure. In contrast, the carboxy-terminal 22-52 and 40-52 amino acid fragments had no consistent vasodilator activity. After administration of the nitric oxide synthase inhibitors, N omega-nitro-L-arginine benzyl ester or N omega-nitro-L-arginine methyl ester (L-NAME), pulmonary vasodilator responses to ADM, to ADM15-52, to CGRP, to acetylcholine, and to bradykinin were significantly decreased in the rat, whereas vasodilator responses to isoproterenol and nitroglycerin were not changed. However, in the pulmonary vascular bed of the cat, L-NAME had no significant effect on vasodilator responses to ADM in doses that attenuated vasodilator responses to acetylcholine and bradykinin. L-NAME had no effect on responses to isoproterenol or nitric oxide. When the relative vasodilator activity of the active peptides was compared, ADM15-52 was approximately three-fold less potent than ADM, and ADM was threefold less potent than CGRP in decreasing pulmonary vascular resistance in the rat lung. When vasodilator responses were compared in the rat and cat, ADM was threefold more potent in decreasing pulmonary vascular vascular resistance in the cat than in the rat, and vasodilator responses to ADM were independent of the intervention used to raise tone in the rat. The present data demonstrate that ADM and ADM15-52 have significant vasodilator activity in the pulmonary vascular bed of the rat, and that responses to ADM, ADM15-52, and CGRP are dependent on the release of nitric oxide in the rat. The present results indicate that pulmonary vasodilator responses to ADM are not dependent on the release of nitric oxide in the cat and suggest that responses to the peptide are mediated by different mechanisms in the pulmonary vascular bed of the rat and cat.

The search for synthetic analogues of somatostatin (SRIF) which exhibit selective affinities for the five known receptor subtypes (sst1-5) has generated a large number of potent agonist analogues. Many of these agonists display good subtype selectivities and affinities for the subtypes 2, 3, and 5, with very few selective for sst1 or sst4. Until the recent report by Bass and co-workers (Mol. Pharmacol. 1996, 50, 709-715; erratum Mol. Pharmacol. 1997, 51, 170), no true antagonists of somatostatin had been discovered, let alone any displaying differential receptor subtype selectivity. In this present study, we further explore the effect of this putative L,5D6 antagonist motif on somatostatin octapeptide analogues with a cyclic hexapeptide core. The most potent antagonist found to date is H-Cpa-cyclo[DCys-Tyr-DTrp-Lys-Thr-Cys]-Nal-NH2, PRL-2970 (21), which has an IC50 of 1.1 nM in a rat pituitary growth hormone in vitro antagonist assay versus SRIF (1 nM). This analogue bound to cloned human somatostatin subtype 2 receptors with a Ki of 26 nM. The highest hsst2 affinity analogue was H-Cpa-cyclo[DCys-Pal-DTrp-Lys-Tle-Cys]-Nal-NH2, PRL-2915 (15), with a Ki of 12 nM (IC50 = 1.8 nM). This analogue was also selective for hsst2 over hsst3 and hsst5 by factors of 8 and 40, respectively, and had no agonist activity when tested alone at concentrations up to 10 microM. Regression analysis of the binding affinities versus the observed antagonist potencies revealed high correlations for hsst2 (r = 0.65) and hsst3 (r = 0.52) with a less significant correlation to hsst5 (r = 0.40). This is quite different from the somatostatin agonist analogues which show a highly significant correlation to hsst2 (r > 0.9). Receptor-selective somatostatin antagonists should provide valuable tools for characterizing the many important physiological functions of this neuropeptide.

Magnetic resonance (MR) images of 21 patients who had undergone radiation therapy were analyzed and compared with those of 15 patients who had untreated tumors. T2-weighted images (TR = 1,500 msec, TE = 90 msec) were most helpful in distinguishing recurrent tumor from radiation fibrosis. Radiation fibrosis, like muscle, usually remained low in signal intensity on T2-weighted images, while tumor demonstrated higher signal intensity. In no patient was the signal intensity of tumor the same or less than muscle on the T2-weighted images. However, relatively high signal intensity on T2-weighted images is not specific for tumor recurrence and may be seen in acute radiation pneumonitis, infection, hemorrhage, and even pulmonary radiation fibrosis.

The search for synthetic analogues of somatostatin (SRIF) which exhibit selective affinities for the five known receptor subtypes (sst1-5) has generated a large number of potent agonist analogues. Many of these agonists display good subtype selectivities and affinities for the subtypes 2, 3, and 5, with very few selective for sst1 or sst4. Until the recent report by Bass and co-workers (Mol. Pharmacol. 1996, 50, 709-715; erratum, Mol. Pharmacol. 1997, 51, 170), no true antagonists had been discovered, let alone any displaying differential receptor subtype selectivity. In this present study, we explore the effect of this putative L5,D6 antagonist motif on various series of somatostatin agonist analogues, both linear and cyclic. It was found that many D5,L6 agonists could be converted into competitive antagonists by applying this motif, the most potent of which was H-Nal-cyclo[DCys-Pal-DTrp-Lys-Val-Cys]-Nal-NH2 (32). This antagonist was selective for hsst2 with an affinity of 75 nM and an IC50 of 15.1 nM against SRIF-14 in a rat in vitro antagonist bioassay. Receptor-selective somatostatin antagonists should provide valuable tools for characterizing the many important physiological functions of this neuropeptide.

The search for synthetic peptide analogues of somatostatin (SRIF) which exhibit selective affinities for the five known receptor subtypes (sst1-5) has generated a large number of potent agonists. Some of these agonists display good subtype selectivities and affinities for the subtypes 1, 2, 3, and 5, including analogues created by N-methyl amino acid substitutions in a standard octapeptide analogue format. We have now extended this peptide backbone N-methylation approach to a potent somatostatin receptor antagonist series using the antagonist Cpa-cyclo(DCys-Pal-DTrp-Lys-Thr-Cys)-Nal-NH2 9 reported from this laboratory as the lead structure. Synthetic analogues were tested for their ability to inhibit somatostatin-stimulated GH release from rat pituitary cells in culture and to displace 125I-labeled somatostatin from CHO cells transfected with the five known human somatostatin receptors. Several interesting observations resulted from the study. N-Methylation at the Lys(9) residue (5) increased the rat GH release inhibitory potency nearly 4-fold to 0.73 nM but resulted in little change in the binding affinity for human type 2 receptor. This analogue also had a high affinity of 5.98 nM for sst5 receptor (compared to 1.4 nM for somatostatin itself) and is the first antagonist analogue to be reported with high affinity for sst5. It also had high potency on in vitro inhibition of sst5 mediated intracellular calcium mobilization. These results were considered surprising, since the Lys(9) residue has long been considered to constitute the active center of somatostatin, important both for receptor binding and activation, and suggests important conformational differences between D-Cys(9) somatostatin antagonists and normal agonist structures. More modifications were carried out on this analogue with the aim of improving antagonist potency and/or specificity. Tyr(7) substitution of 5 resulted in an analogue, which had the highest affinity in the series for hsst2 (K(I) 5.51 nM) and an extraordinarily low IC50 of 0.53 nM in the rat pituitary cell assay. However, this analogue lost considerable affinity for sst5 relative to analogue 5. Analogue 16 with DTrp(12) at C-terminus had the highest affinity for hsst2, however, the IC50 in the rat GH release assay was only 11.6 nM. Replacement of Lys(9) in 9 with Dab(9) gave 11 which displayed high binding affinity for sst3, and it was also quite selective for that receptor. Both the sst3 and sst5 antagonists should be of value in assigning the physiological roles to type 3 and 5 receptor, respectively.

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