PROSTAGLANDIN AND RENAL FUNCTION

I. The Effect of Prostaglandin A₂ on the PSP Excretion

Abstract

We investigated the effect of prostaglandin (PG) on the renal function in order to study the physiological roles of PG. In this paper we report the effect of the administration of PGA₂ (0.4μg/kg/min) on the renal blood flow.
The infusion of PGA₂ started 5 minutes prior to the injection of PSP, and continued for twenty minutes. All the subjects did not have any disturbances of passage through the upper urinary tracts, edema, or hematuria. The renal blood flow was estimated from the PSP excretion value in 15 minutes, as the latter value has a very high correlation with the former value. At the same time, the change in the urine volume caused by the administration of PGA₂ was also measured.
The results thus obtained are as follows:
1) The administration of PGA₂ caused a 23.8% increase in PSP excretion value in 15 minutes (n=32, p<0.001), and a 77.2% increase in the urine volume in 29 cases (n=29, p<0.01).
2) Based on their control PSP excretion values in 15 minutes, the subjects were divided into four groups; that is, a)≤15%, b) 15%<≤25%, c) 25%<≤35%, and d) 35%<. The rates of increase in PSP excretion value in these groups were 87% (n=2), 38% (n=7), 21% (n=12), and 5% (n=11), respectively. Thus, the subjects with lower PSP values, hence with worse renal function, showed a better response to PGA₂ (p<0.01). The identical tendency was observed in the increase in the urine volume.
3) The subjects were, then, divided into five groups according to their funduscopic findings; namely, a) normal, b) KW_I, c) KW_IIa, d) KW_IIb, and e) KW_IIc. The rates of increase in PSP excretion value in these groups were 12% (n=), 31% (n=6), 32% (n=4), 20% (n=2), and 34% (n=4), respectively. Although statistically not significant, the groups with abnormal funduscopic findings revealed a better response to PGA₂. Almost the same tendency was observed in the increase of the urine volume.
4) The subjects were further divided into three groups as follows; a) the normotensive, b) the mild hypertensive who do not use depressants, and c) the relatively severe hypertensive whose hypertension was persistent even under the administration of drugs. The group with relatively severe hypertension showed a higher increase in PSP excretion than the groups with normotension and mild hypertension (p<0.05). The groups with hypertension regardless of their severeness were observed to have the tendency to a greater increase in the urine volume than the group with normotension.
From the results and the observations mentioned avove, we conclude that the renal vascular bed is highly sensitive to PGA₂. This was drawn from the fact that the increase in PSP excretion value in 15 minutes was remarkable while the decrease of the blood pressure was not observed. The subjects with lower PSP excretion values in 15 minutes showed higher rates of increase in PSP excretion.
Therefore, it seems that the more serious the pathologic state of blood vessels, the more sensitive to PG. Thus, these observations may naturally lead one to recognize both the physiological and the clinical importance of PG.