Proteins of the kallikrein-kinin system in human semen. Isolation and properties of kininase II

Mitigation of radiation induced pulmonary vascular injury by delayed treatment with captopril

BACKGROUND AND OBJECTIVE

A single dose of 10 Gy radiation to the thorax of rats results in decreased total lung angiotensin-converting enzyme (ACE) activity, pulmonary artery distensibility and distal vascular density while increasing pulmonary vascular resistance (PVR) at 2 months post-exposure. In this study, we evaluate the potential of a renin-angiotensin system (RAS) modulator, the ACE inhibitor captopril, to mitigate this pulmonary vascular damage.

METHODS

Rats exposed to 10 Gy thorax only irradiation and age-matched controls were studied 2 months after exposure, during the development of radiation pneumonitis. Rats were treated, either immediately or 2 weeks after radiation exposure, with two doses of the ACE inhibitor, captopril, dissolved in their drinking water. To determine pulmonary vascular responses, we measured pulmonary haemodynamics, lung ACE activity, pulmonary arterial distensibility and peripheral vessel density.

RESULTS

Captopril, given at a vasoactive, but not a lower dose, mitigated radiation-induced pulmonary vascular injury. More importantly, these beneficial effects were observed even if drug therapy was delayed for up to 2 weeks after exposure.

CONCLUSIONS

Captopril resulted in a reduction in pulmonary vascular injury that supports its use as a radiomitigator after an unexpected radiological event such as a nuclear accident.

Purification and characterization of a human bradykinin binding protein from inflammatory cells

Bradykinin (BK) is a potent mediator with a broad spectrum of pharmacological and inflammatory actions which are exerted through cell surface receptors. We report here the affinity chromatographic purification of a novel 14 kDa BK binding protein from human blood neutrophils and also peripheral blood mononuclear cells (PBMC), 80% of which are lymphocytes. Radioreceptor crosslinking experiments using bifunctional crosslinkers and radiolabelled BK identified a 14 kDa protein in these cell types both on the cell surface, in glycerol purified plasma membranes and in detergent solubilized cell extracts. Purification by BK affinity chromatography from a variety of BK responsive human cell types i.e. CCD-16Lu lung fibroblasts, HL60 promyelocytes, U937 myelomonocytes and Jurkat T lymphocytes also demonstrated a 14 kDa protein. Purified material obtained from three different BK affinity columns all demonstrated three major proteins at 190, 50 and 14 kDa when eluted with either excess BK or mild acid. Neutrophil fractions from detergent solubilized cell extracts contained an additional 150 kDa protein when eluted with mild acid. Neutrophil and PBMC crude plasma membrane BK affinity column purifications yielded only a single 14 kDa protein. Radioreceptor dot assays of the purified neutrophil eluates containing the 14 kDa protein revealed specific binding to [125I]-BK with a 160 fold excess signal ratio over the original membrane extract. Our data indicates that we have successfully isolated a 14 kDa novel human BK specific binding protein expressed on the surface of inflammatory cells.

Influence of bradykinin antagonists on the motility of human spermatozoa enhanced by bradykinin

Washed human spermatozoa were coincubated at a constant concentration of bradykinin (BK) (10(-8) M) with different concentrations of the bradykinin antagonists Hoe 140, (Thi5,8, D-Phe7)-BK, and D-Arg(Hyp3, D-Phe7)-BK. In the range between 10(-10) and 10(-5) M none of the tested bradykinin antagonists was able to decrease significantly sperm motility enhanced by addition of 10(-8) M BK. Although bradykinin as the terminal effector of the kallikrein-kinin system stimulates sperm motility specifically and at low concentrations, the specific kinin antagonists failed to inhibit the effect of BK. It would appear that the action of bradykinin on motility of human spermatozoa is mediated by a highly specific mechanism. However, in contrast to earlier hypotheses, it is probably not mediated by a specific bradykinin receptor.