Kallikrein-like amidase activity in renal ischemia and reperfusion

We assessed a kallikrein-like amidase activity probably related to the kallikrein-kinin system, as well as the participation of leukocyte infiltration in renal ischemia and reperfusion. Male C57BL/KSJmdb mice were subjected to 20 or 60 min of ischemia and to different periods of reperfusion. A control group consisted of sham-operated mice, under similar conditions, except for ischemia induction. Kallikrein-like amidase activity, Evans blue extravasation and myeloperoxidase activity were measured in kidney homogenates, previously perfused with 0.9 percent NaCl. Plasma creatinine concentration increased only in the 60-min ischemic group. After 20 min of ischemia and 1 or 24 h of reperfusion, no change in kallikrein-like amidase activity or Evans blue extravasation was observed. In the mice subjected to 20 min of ischemia, edema was evident at 1 h of reperfusion, but kidney water content returned to basal levels after 24 h of reperfusion. In the 60-min ischemic group, kallikrein-like amidase activity and Evans blue extravasation showed a similar significant increase along reperfusion time. Kallikrein-like amidase activity increased from 4 nmol PNA mg protein-1 min-1 in the basal condition to 15 nmol PNA mg protein-1 min-1 at 10 h of reperfusion. For dye extravasation the concentration measured was near 200 µg of Evans blue/g dry tissue in the basal condition and 1750 µg of Evans blue/g dry tissue at 10 h of reperfusion. No variation could be detected in the control group. A significant increase from 5 to 40 units of DAbs 655 nm g wet tissue-1 min-1 in the activity of the enzyme myeloperoxidase was observed in the 60-min ischemic group, when it was evaluated after 24 h of reperfusion. Histological analysis of the kidneys showed migration of polymorphonuclear leukocytes from the vascular bed to the interstitial tissue in the 60-min ischemic group after 24 h of reperfusion. We conclude that the duration of ischemia is critical for the development of damage during reperfusion and that the increase in renal cortex kallikrein-like amidase activity probably released from both the kidney and leukocytes may be responsible, at least in part, for the observed effects, probably through direct induction of increased vascular permeability.

Kallikrein-like amidase activity in renal ischemia and reperfusion.

We assessed a kallikrein-like amidase activity probably related to the kallikrein-kinin system, as well as the participation of leukocyte infiltration in renal ischemia and reperfusion. Male C57BL/KSJmdb mice were subjected to 20 or 60 min of ischemia and to different periods of reperfusion. A control group consisted of sham-operated mice, under similar conditions, except for ischemia induction. Kallikrein-like amidase activity, Evans blue extravasation and myeloperoxidase activity were measured in kidney homogenates, previously perfused with 0.9% NaCl. Plasma creatinine concentration increased only in the 60-min ischemic group. After 20 min of ischemia and 1 or 24 h of reperfusion, no change in kallikrein-like amidase activity or Evans blue extravasation was observed. In the mice subjected to 20 min of ischemia, edema was evident at 1 h of reperfusion, but kidney water content returned to basal levels after 24 h of reperfusion. In the 60-min ischemic group, kallikrein-like amidase activity and Evans blue extravasation showed a similar significant increase along reperfusion time. Kallikrein-like amidase activity increased from 4 nmol PNA mg protein-1 min-1 in the basal condition to 15 nmol PNA mg protein-1 min-1 at 10 h of reperfusion. For dye extravasation the concentration measured was near 200 microg of Evans blue/g dry tissue in the basal condition and 1750 microg of Evans blue/g dry tissue at 10 h of reperfusion. No variation could be detected in the control group. A significant increase from 5 to 40 units of DeltaAbs 655 nm g wet tissue-1 min-1 in the activity of the enzyme myeloperoxidase was observed in the 60-min ischemic group, when it was evaluated after 24 h of reperfusion. Histological analysis of the kidneys showed migration of polymorphonuclear leukocytes from the vascular bed to the interstitial tissue in the 60-min ischemic group after 24 h of reperfusion. We conclude that the duration of ischemia is critical for the development of damage during reperfusion and that the increase in renal cortex kallikrein-like amidase activity probably released from both the kidney and leukocytes may be responsible, at least in part, for the observed effects, probably through direct induction of increased vascular permeability.

Renal ischemia-induced increase in vascular permeability is limited by hypothermia.

The purpose of the present work was to evaluate the kallikrein-kinin system and effects of hypothermia during renal ischemia and reperfusion. Male C57BL/KSJmdb mice were subjected to 20 or 60 min ischemia for different periods of reperfusion. Our results demonstrate that short periods of ischemia followed by reperfusion did not cause significant alterations in kallikrein activity, Evans Blue (EB) extravasation, prokallikreins, myeloperoxidase activity or plasma creatinine concentration. Edema was evident at 1 h reperfusion in the treated mice, but returned to basal values after 24 h reperfusion. Kallikrein activities and EB extravasation showed a significant increase in 60 min ischemic mice. Myeloperoxidase activity in the kidney of the mice confirmed net infiltration in the group with 60 min ischemia and 24 h reperfusion. The generation of kinins and activation of matrix degrading enzymes by tissue kallikrein, liberated from both renal and infiltrated leukocytes, could be responsible at least in part for the damage observed in the kidney of mice subject to 60 min ischemia and reperfusion. The hypothermia significantly reduced the inflammatory process in the 60 min ischemic mice, and did prevent an increase in vascular permeability. Nevertheless, the tissue edema was not shown to change between normothermic and hypothermic ischemic mice.

The involvement of kallikrein-kinin system in diabetes type I (insulitis).

Islet inflammation or insulitis is followed by selective destruction of the insulin secreting B-cell. Animal models of insulin-dependent diabetes mellitus (IDDM) have been used to characterize more fully insulitis, and our results with C57/BL/Ks mdb with low doses of streptozotocin (STZ) confirmed the disease. B1 receptor antagonist [Leu8]des-Arg9-BK has shown a significant effect on diabetic glycemia and renal control parameters. Compared to insulin, the drug was effective to prevent the insulitis and the renal damage. On the other hand, B2 receptor antagonist (HOE 140) and ACE-I (captopril) were only able to control the urinary diabetic proteinuria.

Constitutive nitric oxide synthase (cNOS) activity in Langerhans islets from streptozotocin diabetic rats.

Nitric oxide synthase activity was measured in Langerhans islets isolated from control and streptozotocin diabetic rats. The activity of the enzyme was linear up to 150 micrograms of protein from control rats and was optimal at 0.1 microM calcium, when it was measured after 45 min of incubation at 37 degrees C in the presence of 200 microM arginine. Specific activity of the enzyme was 25 x 10(-4) nmol [3H]citrulline 45 min-1 mg protein-1. Streptozotocin diabetic rats exhibited less enzyme activity both in total pancreas homogenate and in isolated Langerhans islets when compared to control animals. Nitric oxide synthase activity measured in control and diabetic rats 15 days after the last streptozotocin injection in the second group of animals corresponded only to a constitutive enzyme since it was not inhibited by aminoguanidine in any of the mentioned groups. Hyperglycemia in diabetic rats may be the consequence of impaired insulin release caused at least in part by reduced positive modulation mediated by constitutive nitric oxide synthase activity, which was dramatically reduced in islets severely damaged after streptozotocin treatment.

Constitutive nitric oxide synthase (cNOS) activity in Langerhans islets from streptozotocin diabetic rats

Nitric oxide synthase activity was measured in Langerhans islets isolated from control and streptozotocin diabetic rats. The activity of the enzyme was linear up to 150 mug of protein from control rats and was optimal at 0.1 muM calcium, when it was measured after 45 min of incubation at 37ºC in the presence of 200 muM arginine. Specific activity of the enzyme was 25 x 10(-4) nmol [3H] citrulline 45 min(-1) mg protein(-1). Streptozotocin diabetic rats exhibited less enzyme activity both in total pancreas homogenate and in isolated Langerhans islets when compared to control animals. Nitric oxide synthase activity measured in control and diabetic rats 15 days after the last streptozotocin injection in the second group of animals corresponded only to a constitutive enzyme since it was not inhibited by aminoguanidine in any of the mentioned groups. Hyperglycemia in diabetic rats may be the consequence of impaired insulin release caused at least in part by reduced positive modulation mediated by constitutive nitric oxide synthase activity, which was dramatically reduced in islets severely damaged after streptozotocin treatment.