Elevated expression of adenosine A1 receptor in bronchial biopsy specimens from asthmatic subjects

Asthmatics, unlike healthy subjects, experience bronchoconstriction in response to inhaled adenosine, and extracellular adenosine concentrations are elevated in the bronchoalveolar lavage fluid and exhaled breath condensate of asthmatic subjects. However, little is known about the location and expression of adenosine receptors in asthmatic airways. The aim of the present study was to investigate the distribution of adenosine A(1) receptors in bronchial biopsy specimens from mildly asthmatic steroid-naïve subjects and then compare the degree of expression with that of healthy subjects. Biopsy sections were immunostained using an adenosine A(1) receptor antibody, the selectivity of which was validated in specific experiments. Image analysis was then performed in order to determine differences in immunostaining intensity. Immunostaining of biopsy sections from the asthmatic subjects revealed strong expression of the A(1) receptor, located predominantly in the bronchial epithelium and bronchial smooth muscle. In comparison, very weak immunostaining was observed in biopsy specimens obtained from healthy subjects. Image analysis revealed that the intensity of positive staining of the asthmatic bronchial epithelium and smooth muscle regions was significantly greater than that observed for the healthy epithelium and smooth muscle. In conclusion, the sensitivity of asthmatics to inhaled adenosine coupled with increased adenosine A(1) receptor expression implies that these receptors play a role in the pathophysiology of this disease.

Potent antagonism by BIM-23056 at the human recombinant somatostatin sst5 receptor

We have investigated the effects of somatostatin (SRIF) and the linear octapeptide BIM-23056 on changes in intracellular calcium ion concentration ([Ca2+]i) and on the formation of inositol-1,4,5-trisphosphate (Ins(1,4,5)P3) in CHO-K1 cells transfected with the human recombinant SRIF sst5 receptor. SRIF elicited concentration-dependent increases in [Ca2+]i, with a pEC50 of 7.02 +/- 0.06, while BIM-23056 (1 x 10(-7) M) behaved not as an agonist but as a potent, surmountable antagonist of these increases in [Ca2+]i. The SRIF concentration-effect curve for increases in [Ca2+]i was shifted rightward producing an estimated pKB for the antagonist of 8.0. BIM-23056 (1 x 10(-7) M) also significantly attenuated Ins(1,4,5)P3 increases due to SRIF, but had no effect on either basal or uridine 5'-triphosphate (UTP) (1 x 10(-4) M) stimulated increases in the levels of [Ca2+]i or Ins(1,4,5)P3.