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ARTICLES
Year : 1986  |  Volume : 34  |  Issue : 1  |  Page : 53-56

The effect of prostaglandins E1 and F2a on intraocular and arterial pressure


Department of Physiology, Medical College, Rohtak, India

Correspondence Address:
Pardaman I Singh
6/6J, Medical College, Rohtak-124001
India
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Source of Support: None, Conflict of Interest: None


PMID: 3481771

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How to cite this article:
Khurana I, Singh PI, Maini B K, Khurana A K. The effect of prostaglandins E1 and F2a on intraocular and arterial pressure. Indian J Ophthalmol 1986;34:53-6

How to cite this URL:
Khurana I, Singh PI, Maini B K, Khurana A K. The effect of prostaglandins E1 and F2a on intraocular and arterial pressure. Indian J Ophthalmol [serial online] 1986 [cited 2020 Feb 20];34:53-6. Available from: http://www.ijo.in/text.asp?1986/34/1/53/26342

Table 2

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Table 2

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Table 1

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Table 1

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Various closely related compounds of PG based on conlgaration of the cyclopentane ring have been isolated (PGE1, PGE2, PGF1a, PGF2a). Although the effects of the compounds on ocular tissues and on the cardiovascular system have been studied in different animal species[1],[2] there are very few reports on comparative studies of PGE and PGF compounds in the same group of animals In the present investigation we have compared the effect of PGEI and PGF­2a on intraocular pressure (IOP) and arterial blood pressure (ABP).


  Materials and methods Top


Eight male, albino rabbits, varying in age from 1.5 to 2 years, and weighing approxi­mately 2kg each were anaesthetised with intravenous ntmbutal (40mg/kg body weight) The femoral vein was cannulated for the infusion of drugs, and the femoral artery was cannulated for recording of arterial pressure. A pressure transducer was filled with beparinized saline and connected to the strain gauge input of a two channel recorder (Polyrite INCO).

The intraocular pressure was measured through a 26 guage needle inserted into the anterior chani'ber (at 12'o clock position) and connected via a polythene tube to a pressure transducer. A two channel recorder was used for simultaneous recording of IOP (first channel) and arterial pressure (second channel). A time signal was recorded at one second intervals.

Basal IOP and ABP were recorded and the effects of intravenous infusion of PGE1 and PGF2a (single dose) measured. Stock solutions of PGE1 and of PGF2a were pre­pared in phosphate buffer at ph 7.9 as des­cribed by Waitzman and King[3] and were stored in a freezer. They were diluted to the desired concentration in 0.9% saline immediately before use.

PG was injected into the marginal vein of the rabbit's ear in graded doses (0.2, 0.5, 1, 5, 10 and 20 ug). An interval of five minutes was given between the infusion of each dose. The effect on blood pressure and IOP was observed. The infusion of PGEI and PGF2a produced a fall in blood pressure within 2 to 3 seconds, whereas the rise in IOP took place after 10 to 15 seconds. Before injecting each test dose the ABP was allowed to normalize. However, the IOP showed a steady rise with each successive dose of PGE1 or of PGF2a and was not normalized.


  Observations Top


Effect of PGEI and PGF2a on IOP

The mean values for the increase in IOP produced by intravenous infusion of PGE1, and of PGF2a, are given in [Table - 1] and in [Figure - 1]. The IOP showed a sustained rise with increasing doses of both PGE1 and PGF 2a. However, as is obvious from [Figure - 1], the effect was more marked with PGF2a. The mean value for resting TOP was 18 93 ± 2 21 mm Hg. The maximum increase with PGEI infusion was 26.00 3.60 mm Hg; and with PGF2a it was 26.25 ± 2.9U mm Hg. With either prostaglandin the threshold dose for producing an increase in IOP was 0.2ug. The value of the correlation coefficient was higher for PGEI (r=0.75) as compared to PGF2a (r=0.e8). The value of the slope was also higher for PGE1 (b=0.24) as com­pared to PGF2a (b=0.20). When the diffe­rences in the mean responses produced by individual doses of PGE1 and PGF2a are compared it is seen that the mean response is in each case greater for PGF2a : however, the differences are significant (paired t-test) for dose levels lug and 2 ug, but not at others. The significance of the results for all dose levels taken together (calculated by using the multiplication law of probability) is much less than <0.001 showing that the differences are very highly significant.

Effect of PGEI and PGF2a on Arterial Blood Pressure

The mean values of both systolic blood pressure (SBP) and of diastolic blood pressure (DBP) are given in [Table - 2]. With infusion of graded doses of PGEI and PGF2a, there was gradual decrease in both SBP and DBP [Figure - 2]. However, the blood pressure lower­ing effect of PGE1 was greater than that of PGF2a (p <0.001 at each dose level).


  Discussion Top


The influence of postaglandins in increas­ing intraocular pressure is well documented. The effect can be demonstrated after intra­cameral injection[3], after topical application[4], or after intravenous -administration[5],[6].

The depressor effect of prostaglandins on blood pressure is also well known[1], both in respect of PGE1[6],[7] and in respect of PGF2a[8]. It has been suggested that the hypotensive effect of PGF2a is due to decrease in peri­pheral resistance as a result of a vasodilator effect[9],[10]; and that this is associated with vegal activation[9]. In contrast the bypoten­sive effect of PGEI is said to occur indepen­dent of peripheral autonomic mechanisms[11]. Keeping this background in view it becomes interesting to make a comparative evaluation of the effects of different prostaglandins. Because of the presence of species variations, the responses produced by different postag­landins can be validly compared only if they are tested in the same group of animals. There are hardly any such studies.

In the present study we have compared the effects of PGE1 and PGF2a in the same group of animals. It is clearly demonstrated that PGF is more potent than PGEI in raising IOP, whereas in the case of blood pressure the effect of PGEI is more pronoun­ced than that of PGF2a.


  Summary Top


The effect of intravenous infusion of prostaglandin E1 (PGE1) and of postaglandin F2a (PGF2a) was studied in rabbits. The IOP showed a rise both with PGE1 and PGF2a : however, the effect produced was significantly greater with PGF2a The increase in IOP was dose dependant. The threshold dose required to produce an effect was 0.2 ug. Thereafter, there was a linear relationship between the dose administered and increase in IOP up to a dose of 5 ug with higher dosage the increase in IOP was less marked.

Both PGE1 and FGF2a lowered systolic as well as diastolic blood pressure. Fall in blood pressure was related to the dose administered. The blood pressure lowering effect of PGE1 was significantly greater than that of PGF2a.

 
  References Top

1.
Karim, S.M.M., 1976, Prostaglandins : Physio­logical, Pharmacological and pathological aspects, Publisher-R & R Clark Ltd. Edinburgh, p. 104.  Back to cited text no. 1
    
2.
Anggard, E. and Bergstrom, S., 1963, Acta Physiol Scand, 58:1.  Back to cited text no. 2
    
3.
Waitzman, M.B. and King, C.D., 1967, Amer J Physiol, 212:329.  Back to cited text no. 3
    
4.
Bethel, R.A. and Eakins, K. E. , 1972, Exp. Eye Res, 13:83.  Back to cited text no. 4
    
5.
Starr, M., 1971, Exp. Eye Res. 11:170.  Back to cited text no. 5
    
6.
Chiang, T.S., Thomas, R.P., 1972, Arch. Ophthalmol 88:418.  Back to cited text no. 6
    
7.
Horton, E.W. and Main, I.H.M., 1963, Brit J. Pharmac. 21:182.  Back to cited text no. 7
    
8.
Levy, B and Lindner, H.R , 1971, Brit J Phar­mac. 43:236.  Back to cited text no. 8
    
9.
Nakano, J., Chang, A.C.K. and Fischer, R.G., 1973, J. Neurosurg. 38:32.  Back to cited text no. 9
    
10.
Beck, L,, Pollard, A,A., Kayaalp, S.O. and Weiner, L.M., 1966, Fed Proc. 25:1596.  Back to cited text no. 10
    
11.
Giles, T.D., Quiroz, A.C and Burch, G.E., 1969, Experimentia, 25:1056.  Back to cited text no. 11
    


    Figures

  [Figure - 1], [Figure - 2]
 
 
    Tables

  [Table - 1], [Table - 2]



 

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