HYDRALAZINE-INDUCED LUPOID SYNDROME

Autoantibodies in untreated and treated essential hypertension. I

Using the indirect immunofluorescence method, autoantibodies (AB) of IgG and IgM classes were investigated in sera from 161 consecutive patients with essential hypertension and compared with those from 78 healthy normotensive subjects of the same composition by age and sex, and without any family history of hypertension. The frequency of one or more AB was as high in 78 untreated (15.3%) as in 83 treated patients (13.0%) and was in the controls 9.0% (n.s.). In the treated patients, the AB were associated with heart involvement (p less than 0.02). In the untreated patients, antinuclear antibodies of IgG class were associated with BP (p less than 0.01) and fundus grading (p less than 0.005). A family history of hypertension was found in 23.5% of the hypertensive males with AB and in 9.0% of the normotensive males (p less than 0.10). These results are discussed in relation to reports of an association of AB with cardiovascular diseases. It is concluded that the presence of AB in essential hypertension is not necessarily due to drug induction.

Prospective study of immune response to hydralazine and development of antideoxyribonucleoprotein in patients receiving hydralazine

To examine the relationship between the immune responses to hydralazine, a drug known to induce systemic lupus erythematosus, and to deoxyribonucleoprotein (DNP) we followed prospectively 21 hypertensive patients treated with hydralazine for the first time. Within one year, antibodies to hydralazine developed in 16 of these patients and anti-DNP in seven of these. In one patient whose serum had a positive antinuclear antibody test prior to treatment, a mild hydralazine systemic lupus erythematosus syndrome developed preceded by rises in the levels of both anti-hydralazine and anti-DNP. Studies by radioimmunoassay on serums of three additional patients, not followed in this study but known to have hydralazine-induced systemic lupus erythematosus, revealed no evidence for either (1) cross-reactivity between anti-DNP and anti-hydralazine or (2) antibodies specific for a hydralazine-DNP complex. In some way, perhaps related to the mechanism by which carrier molecules enhance the immunogenuity of haptens, hydralazine increases the antigenicity of DNP. This effect depends on the development of immunity to hydralazine as well.

Effect of hydralazine and dihydralazine on connective tissue and binding to serum protein

Hydralazine and dihydralazine, chelators of Fe2+, Fe3+ and Mn2+ ions, inhibited collagen biosynthesis in organ culture of chicken embryo tibiae. Both substances inhibited the in vitro hydroxylation of [14C]Pro-labelled protocollagen by protocollagen proline hydroxylase. A decreased incorporation of [14C]-D-glucosamine into glyco- and/or muco-proteins was found under the effect of the two drugs. Dihydralazine, a cationic compound, was bound to DNA and acid mucopolysaccharides (glycosaminoglycans), forming an insoluble complex. Both substances were bound to serum alpha 2-globulin. Subcutaneous injections of dihydralazine in rats produced a local as well as a general toxic effect.