A histochemical method suitable to discriminate free cholesterol from its esters and both from 7-dehydrocholesterol and vitamins D.

The peracetic acid-toluidine blue and the peracetic acid-Schiff reactions as well as the failure of HgCl2-formalin fixative for inhibiting these reactions appears as a very useful method for free cholesterol histochemical detection and to discriminate it from its esters and from some of its metabolic products such as 7-dehydrocholesterol and vitamins D. The cholesterol histochemical detection provided by those reactions appears specific taking into account the findings afforded by spot tests. The peracetic acid-toluidine blue reaction is very suitable for histochemical purposes on tissue sections, since it does not produces tissues damages, it is sensitive and the stained end product is almost insoluble in the solvents frequently used in histological techniques. The previous ribonuclease treatment and methylation are very useful in avoiding the basophil substances interference on the peracetic acid-toluidine blue reaction. The 2,4-dinitrophenylhydrazine carbonyl group blockade is useful to decrease the influence of carbonyl group on the peracetic acid-histological techniques. The previous ribonuclease treatment and methylation are very useful in avoiding the basophil substances interference on the peracetic acid-toluidine blue reaction. The 2,4-dinitrophenylhydrazine carbonyl group blockade is useful to decrease the influence of carbonyl group on the peracetic acid-histological techniques. The previous ribonuclease treatment and methylation are very useful in avoiding the basophil substances interference on the peracetic acid-toluidine blue reaction. The 2,4-dinitrophenylhydrazine carbonyl group blockade is useful to decrease the influence of carbonyl group on the peracetic acid-Schiff reaction. The peracetic acid-toluidine blue reaction is more sensitive and more specific than peracetic acid-Schiff reaction, since the tissues do contain Schiff reactive products unable to be 2,4-dinitrophenylhydrazine blocked which interfere on the results of the latter reaction decreasing its specificity and its sensitivity. The cholesterol histochemical detection based on the peracetic acid-toluidine blue and peracetic acid-Schiff reaction as it is suitable in discriminating free cholesterol from its esters as well as from some of its metabolic products it appears very useful for metabolic studies on tissue sections.