Monoclonal antibodies raised against bovine anti-müllerian hormone: bovine, ovine, and caprine hormones share a set of identical epitopes

Monoclonal antibodies (Mabs) have been raised against purified bovine anti-Müllerian hormone (bAMH) in an effort to obtain nonzoospecific reagents. Although the majority of the resulting hybridomas resembled those obtained previously insofar as they recognized only bovine, ovine and caprine AMH, four others, all immunoglobulin Ms, were directed against an epitope shared with AMH of other species, namely rabbit, pig and cat. Both the zoospecific and the conserved epitopes were located close to the site required for biological activity. It is suggested that the similarity between the immunogenic characteristics of bovine, ovine and caprine AMH is in some way related to the fact that AMH in these species is disseminated in the blood stream and may produce freemartinism.

Persistence of müllerian ducts in male rabbits passively immunized against bovine anti-müllerian hormone during fetal life

A female rabbit was immunized against purified bovine AMH and mated. Booster injections were given at Day 8 of pregnancy to ensure a high titer of anti-AMH antibodies at the time the rabbit fetal testis begins to produce AMH. In three consecutive litters, the immunized female produced a total of 12 males, 9 of which had persistent Müllerian duct derivatives. No other significant abnormalities were detected in these animals, which were compared to the offspring of a control saline-injected female. In particular, testicular morphology was normal in most animals, and serum FSH levels did not differ from controls. This experimental model lends no support to the hypothesis that AMH controls extra-Müllerian events of male sex differentiation, nor that of the existence of a regulatory mechanism for synthesis of AMH by Sertoli cells, but it does not definitely exclude these possibilities, inasmuch as our tentative conclusions are based upon study of only one immunized female.

Insulin receptors and bioresponses in a human liver cell line (Hep G-2)

A newly developed human hepatoma cell line, designated Hep G-2, expresses high-affinity insulin receptors meeting all the expected criteria for classic insulin receptors. 125I-insulin binding is time-dependent and temperature-dependent and unlabeled insulin competes for the labeled hormone with a half-maximal displacement of 1-3 ng/ml. This indicates a Kd of about 10(-10) M. Since Scatchard analysis of the binding data results in a curvilinear plot and unlabeled insulin accelerates the dissociation of bound hormone, these receptors exhibit the negative cooperative interactions characteristic of insulin receptors in many other cell and tissue types. Proinsulin and des(Ala, Asp)-insulin compete for 125I-insulin binding with 4% and 2%, respectively, of the potency of insulin. Anti-(insulin receptor) antibody competes fully for insulin binding. The two insulin-like growth factors, multiplication-stimulating activity and IGF-I are 2% as potent as insulin against the Hep G-2 insulin receptor. Furthermore, Hep G-2 cells respond to insulin in several bioassays. Glucose uptake, glycogen synthase, uridine incorporation into RNA and acetate incorporation into lipid are all stimulated to varying degrees by physiological concentrations of insulin. In addition, these cells 'down-regulate' their insulin receptor, internalize 125I-insulin and degrade insulin in a manner similar to freshly isolated rodent hepatocytes. This is the first available human liver cell line in permanent culture in which both insulin receptors and biological responses have been carefully examined.

Production of anti-Müllerian hormone: another homology between Sertoli and granulosa cells

Anti-Müllerian hormone (AMH) has been detected by RIA in the follicular fluid of mature bovine ovaries and in incubation medium of bovine granulosa cells. Purification of AMH from two independent batches of follicular fluid was achieved with a yield of 11% and 15% respectively. Both ovarian and control testicular AMH produced near-complete regression of fetal rat Müllerian ducts exposed to it in culture at a final concentration of 200-300 mU/ml and were recognized by the same monoclonal and polyclonal antibodies. These findings indicate that adult mammalian granulosa cells are capable of producing immunoreactive and bioactive AMH at a rate apparently similar to that already demonstrated for mature Sertoli cells and add yet another item to the homologies reported between male and female somatic gonadal cells.

Origin of anti-Mullerian hormone in bovine freemartin fetuses

The origin of AMH responsible for Müllerian duct regression in bovine freemartins has been reinvestigated, using a sensitive RIA for this hormone. Between 50 and 80 days, Müllerian duct regression occurs simultaneously in males and freemartins. Both twins exhibited high and positively correlated serum AMH concentrations, whereas gonadal in-vitro production of AMH and biological anti-Müllerian activity were detectable at a low level only in 2 out of 13 freemartins. In the gonads of approximately half the freemartins after 80 days, seminiferous tubules differentiated and the gonads produced AMH, but the output was very low compared to that of the male twin. These data suggest that regression of Müllerian duct in freemartins is essentially mediated by AMH produced by the testes of the male twin.

Use of monoclonal antibody techniques to study the ontogeny of bovine anti-Müllerian hormone

Monoclonal antibodies against bovine anti-Müllerian hormone (AMH) were used to study the hormone in cattle. Anti-Müllerian activity of testicular tissue, immunoreactive testicular AMH, serum AMH concentration and AMH production by incubated testicular tissue were detectable from 42 days, i.e. at the time of seminiferous tubule differentiation, and peaked between 50 and 80 days, when the Müllerian ducts regress in the male fetus. All the values stabilized at a lower level until 30 days after birth and then slowly decreased. At 18 months, only traces of AMH immunoreactivity were detectable in testicular tissue and serum concentration and AMH production by incubated testicular tissue were negligible; the main source of AMH in the adult animal was the rete testis fluid. Study of the disappearance rate of AMH from the serum of castrated calves gave a half-life of approximately 2 days for bovine AMH.

[Anti-mullerian hormone : a new glycoprotein (author's transl)]

The hypothesis that anti-müllerian hormone might be a glycoprotein was suggested by the discrepancy between various methods of evaluation of the molecular weight of the substance responsible for anti-müllerian activity. Incorporation of radioactive fucose to the proteins synthesised by the fetal calf testis in vitro resulted in specific labelling of bioactive molecules, once labelled contaminants had been removed by prior partial purification.

Biosynthesis of labelled anti-müllerian hormone by fetal testes: evidence for the glycoprotein nature of the hormone and for its disulfide-bonded structure

Tritiated fucose incorporated into proteins released by fetal calf tests into incubation medium proved to be a marker for anti-müllerian hormone (AMH) once non-specific glycoproteins had been eliminated by partial purification. When partially purified incubation medium from fetal calf teste s was fractionated by gel filtration, sucrose density gradient sedimentation or preparative electrofocusing, a single radioactive protein peak co-purified with anti-müllerian activity. Partially purified medium from bull testes--which are devoid of anti-müllerian activity--has a much lower fucose content than that derived from fetal testes. Antisera directed against 'fetal'--but not 'bull'--partially purified incubation medium, and capable of blocking anti-müllerian activity, precipitated the radioactive protein peak. The molecular weight of labelled AMH was 215,000 when determined by gel filtration and 124,000 when determined by density gradient sedimentation. By SDS-PAGE the molecular weight of labelled AMH was 123,000 and dissociation into a 72,000 subunit was demonstrated under conditions which reduce disulfide bonds.