SEPARATION AND CHARACTERIZATION OF CYCLIC-NUCLEOTIDE PHOSPHODIESTERASES FROM THE LACRIMAL, HARDERIAN AND ZYGOMATIC GLANDS OF THE RABBIT

Purpose. To investigate the activity profile of cyclic nucleotide phos phodiesterase (PDE) isoenzymes and the effects of isoenzyme selective inhibitors in the superior and inferior lacrimal glands, Harderian gla nd, and zygomatic gland of the rabbit. Methods. Protein fractions extr acted from crude homogenates on an anion exchange column were examined for PDE activity using an HPLC method for detecting nucleotides. Resu lts. The superior and inferior lacrimal glands had identical PDE activ ity profiles. PDE I was the major type of activity and there was also a minor PDE III peak of activity. The main activity detected in the li pid secreting Harderian gland was PDE II and for the mucus secreting z ygomatic gland PDE m. All glands contained PDE IV activity. The kineti cs of the peak enzyme activities were examined and found similar, but not identical to the kinetics for PDE activities obtained from other t issues. Inhibitors of specific PDE classes and the general PDE inhibit or, IBMX, were tested on the peak enzyme activities. Activities design ated by their substrate specificity or co-factor modification were mos t strongly inhibited by the corresponding class selective inhibitor. F or example, PDE I activity in the lacrimal gland was most strongly inh ibited by nicardipine. All activities were inhibited by IBMX. Conclusi ons. The superior and inferior lacrimal glands of the rabbit have the same PDE profile and this differs from the PDE subtypes detected in th e mucus secreting zygomatic gland and the lipid secreting Harderian gl and.