IMMUNOSUPPRESSIVE ACTION OF CAPTOPRIL BLOCKED BY PROSTAGLANDIN SYNTHETASE INHIBITOR

1005 elevated. It transpired that blood pressure had been recorded with of the very low reading aneroid instruments. These results emphasise the need for frequent, perhaps monthly, calibration tests on aneroid sphygmomanometers in addition to checks done after each droppage or similar insult-and reinforce the arguments for mercury manometers. one

Department of Physiology, Medical School, University of Bristol,

C. E. BOWMAN

Bristol BS8 1TD

IMMUNOSUPPRESSIVE ACTION OF CAPTOPRIL BLOCKED BY PROSTAGLANDIN SYNTHETASE INHIBITOR

Fetal umbilical vein blood flow and haemoglobin level of the umbilical cord blood in twelve cases of rhesus immunisation.

There may be clinical applications of this non-invasive and rapid method for screening, before the use of more invasive diagnostic procedures, where fetal anaemia is suspected. This examination may also be valuable for the follow-up of fetal well-being after intrauterine therapy in such pregnancies, because it can be repeated without harm to the fetus or mother. Department of Obstetrics and Gynaecology, University of Oulu, Oulu 22, Finland 90220

P. KIRKINEN P. JOUPPILA

Department of Obstetrics and Gynaecology,

Ålesund Central Hospital,

Ålesund, Norway

S. EIK-NES

BLOOD PRESSURE ERRORS WITH ANEROID SPHYGMOMANOMETERS

SIR,-Aneroid blood pressure instruments have become popular because of their conveniehce and robust construction. Consistent accuracy, however, is their Achilles heel. The American Heart Association recommends that such instruments should be checked at least yearly. I have checked all the aneroid sphygmomanometers in use on the acute medical and surgical wards of a major teaching

hospital. A standard mercury column was connected to an inflation bulb and to the aneroid instrument under test via a T connector. The pressure was raised to about 250 mm Hg and lowered by 3-4 mm/s. At readings of 200,150,100, and 50 mm Hg on the standard column the aneroid gauge was read. On at least one test pressure, eleven out of thirteen hand held instruments deviated from true pressure by 5 mm Hg or more; six of these deviated by at least 10 mm and two recorded a full 20 mm Hg low (see table). Five out of ten of the wall mounted instruments read at least 5 mm Hg low. Most of the hand held instruments were clearly unfit for medical practice. The wall mounted instruments were, presumably due to their relative protection, more accurate. On one surgical ward, following an observation round the previous evening, four postoperative patients had their feet 1 Kirkendall WM,

et

al. Recommendations for human blood pressure determination

sphygmomanometers of the sub committee of the American Heart Postgraduate Education Committee Circulation 1980; 62: 1146A.

by

Association

SIR,-The antihypertensive effect of captopril has in part been ascribed to an increase in the plasma concentration of prostaglandin E2,Iand prostaglandin E2 has been reported to suppress mitogen stimulated lymphocytes in vitro,2so there may be an interaction between blood pressure regulation and immunoregulation at the level of prostaglandins. If so, an immunosuppressive effect of captopril should be abolished by pretreatment with indomethacin, a prostaglandin synthetase inhibitor. To test this hypothesis we did an experiment on three healthy volunteers. The immunosuppressive effect of captopril was determined as suppression of H-thymidine incorporation of phytohaemagglutinin stimulated (PHA-P, Difco) lymphocyte cultures. A modification of the micromethod described by Park and Good3was used. With this method lymphocyte cultures can be established very rapidly. Lymphocyte cultures and plasma samples were prepared from blood collected before and 60 min and 240 min after oral captopril 25 mg. The effect on 3H-thymidine uptake by PHA stimulated lymphocytes of autologous plasma (5% in cultures) was tested in a double crossover system. At least 4 days after the first test, indomethacin 25 mg by mouth was given 60 min before captopril, and blood samples were collected as above. The results are given in the table. The immunosuppressive effect of plasma collected 60 and 240 min after captopril was compared with that of plasma obtained before captopril. Without indomethacin pretreatment, plasma collected 60 min after captopril was immunosuppressive (p<0 02), but the immunosuppressive effect had disappeared in plasma 240 min after captopril. The immunosuppressive effect of captopril was completely abolished by pretreatment with indomethacin (p<0 ’001). These results indicate that blood pressure regulating factors may interact with the immune response, and changes in immune response may thus be expected in hypertension, a question raised by Dr Gudbrandsson and colleagues (Feb. 21, p. 406). Perhaps captopril is of special value in the treatment of renal graft recipients, notably those with hypertension. Further evaluation of the immunosuppressive effect of captopril is needed. Section of Nephrology, Department of Medicine, Sahlgren’s Hospital, S-41345 Göteborg, Sweden

S. A. JOHNSEN M. AURELL

1. Swartz

SL, Williams GH, Hollenberg NK, Levine L, Dluky RG, Moore TJ. Captopril-induced changes in prostaglandin production. J Clin Invest 1980; 65:

1257-64. 2. Goodwin JS, Messner RP, Peak GT. Prostaglandin suppression of mitogen-stimulated lymphocytes in vitro.J Clin Invest 1978; 62: 753-60. 3. Park BH, Good RA. A new micromethod for evaluating lymphocyte responses to phytohemagglutinin: quantitative analysis of the function of thymus-dependent cells. Proc Natl Acad Sci 1972; 69: 371-73.

IMMUNOSUPPRESSIVE EFFECT OF PLASMA AFTER CAPTOPRIL ADMINISTRATION

ACCURACY OF WARD ANEROID SPHYGMOMANOMETERS

’Da:a pooled for four test pressures =,.4.need aneroid instruments.

on

thirteen hand held and

on ten

wall

*Reduced compared with measurements without indomethacin pretreatment (p