Abstract

For the past decade, evidence has accumulated which suggests that the resistance of the teeth to dental decay is in part under systemic control. It was shown that the resistance is accomplished through the optimal operation of a dentinal fluid transport mechanism which is believed to be hormonally controlled by the hypothalamic-parotid gland endocrine axis. Although circumstantial evidence for such an endocrine function was strong, the isolation of a parotid hormone which stimulates the dentinal fluid transport mechanism remained to be accomplished.

Using modern biochemical techniques, a methodology was designed to isolate and purify the hormone from porcine parotid glands. An acetone-dried powder was prepared from fresh parotid tissue and its biologic activity was extracted in aqueous solution at pH 7.0 and pH 5.0. The soluble activity was concentrated by ultrafiltration through PM 30 and DM 05 Amicon membranes before being selectively adsorbed on a column of carboxymethyl cellulose Whatman 52 and eluted with a NaCl linear gradient. The hormone activity was further concentrated by gel chromatography on Sephadex G-50. The isolation of the hormone was finally completed by preparative disc electrophoresis in polyacrylamide gel.

The Aβ parotid hormone thus isolated was characterized as a small glycoprotein having a molecular weight of 8,000 and an isoelectric point of 7.50. Its carbohydrate content was estimated at 2% as neutral hexoses. The amino acid composition of the molecule showed a high level of glycine and proline which together accounted for 73% of the residues. Alanine, serine, arginine, glutamic acid and aspartic acid composed the remaining amino acid residues. The amino acid sequence of the first 28 N-residues was determined.

The biologic activity of the Aβ hormone showed stability and resistance to prolonged incubation at 37°C, a short exposure at 82°C and to alternating freezing and thawing.

The lowest effective dose of Aβ hormone capable of stimulating dentinal fluid transport in 28 day old rats was assayed at 9.6 pg of protein. The potential cariostatic effect of the parotid hormone was assessed by using the direct correlation existing between the decrease in number of dentinal ninhydrin reactive areas after 2 weeks and the decrease in caries score obtained after 3 months under the same experimental conditions. Daily injection of purified parotid hormone into intact rats maintained on a cariogenic high sugar diet lowered the ninhydrin score by 55% compared to saline-injected control animals maintained on the same diet. Similar doses of parotid hormone injected into parotidectomized rats under identical experimental conditions were capable of lowering the ninhydrin reactive area count by 46% compared to the saline-injected controls.

Prospective experiments under the same conditions over a period of 3 months are intended in order to fully ascertain the cariostatic effect of the parotid hormone. On the other hand, the availability of pure parotid hormone is making possible the development of a radioimmunoassay that will permit a more comprehensive investigation of the hypothalamic-parotid gland endocrine axis in relationship to the mechanism of resistance to dental decay and to other endocrine functions.

LLU Discipline

Physiology

Department

Physiology

School

Graduate School

First Advisor

John Leonora

Second Advisor

Kenneth A. Arendt

Third Advisor

Raymond G. Hall

Fourth Advisor

Rene Evard

Degree Name

Doctor of Philosophy (PhD)

Degree Level

Ph.D.

Year Degree Awarded

1978

Date (Title Page)

9-1978

Language

English

Library of Congress/MESH Subject Headings

Parotid Gland -- analysis; Dental Caries -- prevention & control

Type

Dissertation

Page Count

xiii; 144

Digital Format

PDF

Digital Publisher

Loma Linda University Libraries

Usage Rights

This title appears here courtesy of the author, who has granted Loma Linda University a limited, non-exclusive right to make this publication available to the public. The author retains all other copyrights.

Collection

Loma Linda University Electronic Theses and Dissertations

Collection Website

http://scholarsrepository.llu.edu/etd/

Repository

Loma Linda University. Del E. Webb Memorial Library. University Archives

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