The benzyl
ester of
hyaluronic acid (
Hyaff 11) is a highly mucoadhesive
polymer and can be processed into
microspheres that can effectively deliver incorporated drugs by closely adhering to the mucosal surface and by protecting the
drug from enzymatic inactivation. In this study,
Hyaff 11 microspheres have been investigated as novel delivery system for the
vaginal administration of
salmon calcitonin (sCT) to ovariectomized rats. Moreover, this particular animal model has been used to evaluate the
biological activity of the
polypeptide after vaginal and I.M. administration by measuring the skeletal effect of sCT. A total of 66 female rats were used: 6 rats served as the basal group; 12 were subjected to
sham operation and left without pharmacological treatment; 48 underwent
bilateral ovariectomy and these were divided at random into four groups of 12 animals. One group was not submitted to pharmacological treatment; another was treated daily with sCT I.M.; in the other two groups, the
hormone was incorporated into
Hyaff 11 microspheres and was daily administered by vaginal route as dry
powder or dispersed in
pessaries. Sixty days after surgery, rats were sacrificed and the proximal third of the right tibia was removed and prepared for histomorphometry. Treatment with sCT, independent of the administration route, largely prevented the bone volume loss of the nontreated ovariectomized group. Prevention mainly depended on the maintenance of the trabecular number and on the increase of the trabecular thickness. Independent of the administration procedure, sCT greatly reduced the increase of
tartrate-resistant acid phosphatase-positive poly- and, particularly, mononucleated osteoclasts found in the nontreated ovariectomized group.(ABSTRACT TRUNCATED AT 250 WORDS)