Renotropic Activity in Ovine Luteinizing Hormone Isoform(s)*

Abstract

Renotropic activity was previously demonstrated in an ovine LH preparation. This preparation was further purified with a series of chromatographic steps, and the fractions were assayed for renotropic activity in vivo by their ability to stimulate [3H]thymidine incorporation into renal DNA of castrated hypophysectomized male rats. A purified preparation could be dissociated by acid treatment into two major constituent subunits, designated alpha and beta, each of which was composed of three microheterogeneous components (subunits alpha 1-3 and beta 1-3) by reverse phase HPLC. Peptide mapping, including amino acid analyses and partial sequencing of the purified peptides, showed that 1) subunits alpha 3 and beta 3 possess the full length of the polypeptide chains, with the same amino acid sequences as those of the corresponding LH subunits alpha and beta, respectively; and 2) subunits alpha 1 and alpha 2 are complexes of three polypeptides which are missing several N-terminal residues from subunit alpha 3. Conversely, subunits beta 1 and beta 2 lack the C-terminal two residues and one residue, respectively, of subunit beta 3. Renotropic activity was not detected in any of the dissociated subunits alone, but association of alpha 1-3 with beta 1-3 reconstituted the hormonal activity with different potencies. In particular, combination of subunits alpha 3 and beta 3 (alpha 3.beta 3) yielded a potent renotropic activity with weak gonadotropic activity. The carbohydrate composition of the purified preparation exhibiting renotropic activity differed from that of a reference oLH preparation, which possessed greater gonadotropic activity but was devoid of renotropic activity. Furthermore, renotropic activity was decreased after removal of sialic acid by treatment with neuraminidase. Thus, the oligosaccharide moieties as well as the amino acid sequences of the subunits may play an important role in the expression of renotropic activity in vivo, these effects over and above those arising from differential metabolic clearance. We conclude that pituitary renotropin represents a novel activity of a LH- isoform(s) and that the posttranslational (or the artificial, i.e. during preparation) modification of the constituent LH subunits may be responsible for modulation of renotropic activity as well as the intrinsic gonadotropic activity.

Two free isoforms of ovine glycoprotein hormone alpha-subunit strongly differ in their ability to stimulate prolactin release from foetal pituitaries

“…Indeed, the lack of an average of three N-terminal amino acid is in keeping with the difference of 400-500 mass units between the major component of the free B (13 514 Da) and both the free A isoform (14 019 Da) and oLH (13 937 Da). This was not specific for the ovine free , since similar heterogeneities in the N-terminal sequences of the LH or FSH -subunits of ovine, porcine and equine species have also been previously reported (Bousfield & Ward 1984, Nomura et al 1988) and attributed to proteolytic degradation.…”

Transient increase in renal epidermal growth factor content after unilateral nephrectomy in the mouse

“…Furthermore, the compensatory renal hyperplasia is more dominant in young than in mature animals (2,3). A possible role of some endocrine factors in the compensatory renal growth has also been re¬ ported (4)(5)(6)(7)(8). Thus, insulin-like growth factor-I increases in the kidney after uninephrectomy and acts as a paracrine factor (9,10).…”

Partial Purification of a Renotropic Activity from Plasma of Uninephrectomized Human Subjects

“…The great variability in DNA synthesis-stimulating activity levels exhibited by serum samples in different cell types shown in that study make it difficult for conclusions to be drawn as to the specificity of serum renotropic factor(s). The interpretation of data assessing the renotropic activity in unextracted plasma are complicated due to the presence in plasma of a variety of regulators (activators and inhibi tors) of renal growth [17][18][19][20], In fact, we observed a broad range of activity values in our subjects' plasma when using plasma concentrations of less than 30% in our tubule assay. These values though were lower than those previously reported by using human kidney cells in the bioassay of plasma [15], suggesting a certain species-specificity of the renotropic activity.…”