AJP - Heart and Circulatory Physiology, Vol 242, Issue 4 602-H610, Copyright © 1982 by American Physiological Society
Immunoreactive glandular kallikrein in rat plasma: a radioimmunoassay for its determination
S. F. Rabito, A. G. Scicli, V. Kher and O. A. Carretero
A radioimmunoassay (RIA) has been developed to measure immunoreactive
glandular kallikrein in rat plasma. To prevent the binding of radioactive
kallikrein to plasma inhibitors, 125I-kallikrein was inactivated with
phenylmethylsulfonyl fluoride (PMSF), a procedure that maintained
125I-kallikrein immunoreactivity. Different volumes of plasma displaced
125I-PMSF-kallikrein in a parallel fashion to the kallikrein standard
curve. The sensitivity of the RIA was 200 pg, and the recovery of
nonradioactive active kallikrein added to plasma was 58.7%. The
concentration of immunoreactive glandular kallikrein in normal rat plasma
averaged 47.1 +/- 1.7 (SE) ng/ml. Bilateral nephrectomy caused a threefold
increase in circulating glandular kallikrein (50 +/- 2.7 to 167 +/- 7
ng/ml; P less than 0.001). REmoval of the submandibular and sublingual
glands significantly decreased its concentration from 52 +/- 2.3 to 34 +/-
1.6 ng/ml (P less than 0.001). Immunoreactive glandular kallikrein was
higher in the submandibular gland vein than in arterial blood (venous: 94
+/- 10.5; arterial: 64 +/- 6.3 ng/ml; P less than 0.05) and was lower in
the renal venous blood (venous: 44 +/- 2.2; arterial: 53 +/- 2.6 ng/ml; P
less than 0.05). In conclusion, this study shows that the use of
125I-PMSF-kallikrein as tracer prevents the interference in the RIA caused
by plasma protease inhibitors. It also indicates that the submandibular
gland is an important source of the immunoreactive glandular kallikrein in
rat plasma and that the kidney probably participates in its metabolism.
Glandular kallikrein released by the submandibular gland into the
circulation may participate in regulating local blood flow before it is
inactivated by plasma inhibitors.
