Gastrin is a major mediator of the gastric phase of acid secretion in dogs: proof by monoclonal antibody neutralization.

We developed a monoclonal antibody, 28.2, that binds specifically to the amidated carboxyl terminal region common to gastrin and cholecystokinin. This immunoglobulin G1 antibody has high affinity (ID50 = 30-70 pM for gastrin and cholecystokinin peptides), binds labeled gastrin similarly at 37 degrees C and 4 degrees C, and shows minimal inhibition of binding in the presence of 40% canine serum. Antibody 28.2 was used to carry out in vivo immunoneutralization studies in 8 dogs previously prepared with chronic gastric fistulas. Preliminary studies revealed that a single intravenous dose of 0.75 mg of partially purified immunoglobulin G of monoclonal antibody 28.2 completely inhibited the acid stimulatory effect of exogenous gastrin-17 given intravenously at 200 pmol/kg.h, a physiologic dose, and inhibited by 70% the acid response to a supraphysiologic dose, 800 pmol/kg.h. The same dose of antibody decreased the acid secretory response obtained during distention of the stomach with 300 ml of 5.8% glucose solution by 98% and decreased the response to distention with 300 ml of 8% peptone solution by 68%. A 10-fold higher dose of antibody decreased the acid response to peptone by 96%. The gastrin antibody had no effect on the acid response to exogenous histamine. A control antibody, specific for the biologically inactive glycine-extended gastrin/cholecystokinin peptapeptide region, had no significant effect on gastric acid secretion stimulated by gastrin or by gastric distention with nutrients. These studies indicate that circulating gastrin is of major importance in the gastric phase of gastric acid stimulation caused by distention of the stomach with nutrients.

Localization of follicle regulatory protein in the porcine ovary.

The granulosa cell secretes a protein (follicle regulatory protein: FRP) that affects the responsiveness of other follicles to gonadotropin stimulation. This protein was purified, partially characterized, and rabbit antisera as well as monoclonal antibodies were prepared against FRP. Fixed sections of porcine ovaries were prepared on slides and then incubated with the monoclonal antibody or polyclonal antisera and then incubated with either biotinylated mouse IgM or rabbit IgG antisera, respectively. These sections were then incubated with avidin conjugated to horseradish peroxidase, followed by substrate. Staining with both the monoclonal antibody and the antisera was present in the cytoplasm of granulosa cells of small- or medium-sized antral follicles. Staining distribution was localized preferentially to cells near the basal lamina; the antral granulosa cells of viable follicles did not stain. Neither primordial follicles nor pre-antral follicles (less than 300 microns in diameter) showed any positive staining. Thecal cells were not stained in follicles less than 5 mm in diameter, whereas some large follicles (greater than 5 mm) contained staining in the theca. In the latter, specific granulosa staining was only weakly positive with the polyclonal antibody and negative with the monoclonal antibody. Atretic follicles contained significant staining of all epithelial cells adjacent to the basal lamina by both the monoclonal and polyclonal antibody preparations. Staining of the luteal ovary by the monoclonal antibody was limited to the large luteal cells. These findings suggest that FRP is produced by the granulosa cells of porcine follicles at the stage of maturation corresponding to 0.5 mm in diameter. As the viable follicle increases in size, production of FRP in the granulosa is reduced below the detectable level when the follicle exceeds 5 mm in diameter. The main source of FRP during the luteal phase is the large cell of the corpus luteum.

Determination of follicle regulatory protein levels in urine during the normal menstrual cycle using an enzyme-linked immunosorbant assay.

A protein from follicular fluid [referred to as follicle regulatory protein (FRP)] which inhibits aromatase activity in granulosa cells was recently isolated and partially characterized. The purified FRP was used to produce a monoclonal antibody which was used to develop an enzyme-linked immunosorbant assay suitable for quantitation of FRP in urine. Twelve normal premenopausal women underwent daily collection of blood and first morning urine samples, beginning on the 1st day of menses, as well as daily ultrasonographic evaluation of follicular diameter, beginning on the 10th day of the menstrual cycle, until the onset of the next menses. Serum estradiol, progesterone, LH, and FSH levels were determined by RIA. Urinary FRP levels increased in the midfollicular phase, reached their zenith in the midluteal phase [mean, 0.38 +/- 0.03 (+/- SE) immunoreactive units; 1 immunoreactive unit = approximately 1 ng FRP/mL.mg creatinine], and then declined to reach their nadir (not detectable) during the early follicular phase. Immunohistochemical evaluation of ovarian tissue demonstrated that anti-FRP localized to mural granulosa cells in viable follicles, to all follicular epithelial cells in atretic follicles, and to the large cells of the corpus luteum. These findings indicate that immunoreactive FRP levels in urine change during the menstrual cycle and suggest a relationship among FRP, follicular maturation, and corpus luteum formation.

Alteration of follicle regulatory protein levels in human reproductive disorders: anovulation.

Recently, a follicle regulatory protein was identified that suppresses ovarian response to gonadotropins. In this study, the serum levels of follicle regulatory protein were measured in five groups of women: reproductive age undergoing oophorectomy (N = 10), postmenopausal (N = 10), ovulatory (N = 13), anovulatory (N = 16), and anovulatory receiving clomiphene citrate therapy (N = 14). Follicle regulatory protein-related immunoreactivity was measured by a competitive enzyme-linked immunosorbent assay, while peripheral estradiol and progesterone levels were determined by established radioimmunoassay. Concentration of follicle regulatory protein in serum in all ovariectomized patients decreased significantly from preoperative levels. The postmenopausal women had significantly lower follicle regulatory protein levels than did ovulatory and anovulatory women. Patients with low levels of serum estradiol in the early follicular phase exhibited either significantly elevated or suppressed follicle regulatory protein levels compared with patients with normal estradiol concentrations, suggesting two different etiologies for ovarian dysfunction. Eleven to 12 and 22-23 days after the onset of the last menstrual period, patients with elevated follicle regulatory protein levels were found to be anovulatory. These observations suggest that elevated intraovarian levels of follicle regulatory protein may cause a disruption of follicular maturation that leads to anovulation and, in some cases, to resistance to clomiphene citrate therapy.