A tan is as much a part of the unofficial Southwestern uniform as a sturdy pair of flip-flops and dark sunglasses.
Beyond its substantial cosmetic appeal, a tan is the body's natural defense against the sun and the ravages of skin cancer.
However, for a tan to occur, skin must be exposed to ultraviolet rays for melanin production. By then, cellular damage has been done.
A pair of synthetic hormones developed at the University of Arizona a decade ago may help reduce the skin damage by speeding up the tanning process — and one of them may even help men who suffer from erectile dysfunction.
A team of UA scientists invented the synthetic hormone that induces a tan without exposing the skin to damage from the sun.
This synthetic hormone comes in two versions called Melanotan and Melanotan II.
Starting with animal experiments in the mid-1980s, the team — headed by UA professor emeritus of chemistry Dr. Victor Hruby — developed a hormone that is analogous to the naturally occurring alpha-melanocyte stimulating hormone (MSH). This hormone stimulates the production of melanin.
Hruby, together with team member and research partner Mac Hadley, UA professor emeritus of anatomy, had been studying this field of chemistry involving hormones and neurotransmitters since 1969.
The naturally occurring hormone that Melanotan is based on is a primordial hormone, Hruby said.
Found in animals from fish to amphibians to humans, MSH has evolved to perform a variety of regulatory activities in the body.
One of the first hormones to have its structure determined, MSH has been found to stimulate more than just pigmenta-tion. It has also been linked with learning behavior, stress levels and appetite.
The MSH hormone was easily degradable and unstable. The researchers' problem lay in creating a version of the hormone that would not be oxidized while in the bloodstream.
The solution resulted in the change of two links in its amino acid structure. MSH contains 13 different amino acids in its chain.
Using a process called total synthesis, the team reconstructed a version of MSH with the substitute amino acids using organic chemistry methods, said Hruby.
With a longer half-life and a thousand times more potency than normal tanning methods, the new synthetic hormone stimulated melanin production far more effectively and rapidly.
In normal situations, melanin production to trigger the body's natural defenses would require sufficient exposure to the sun's ultraviolet rays to damage the skin cells.
The synthetic hormone avoids skin damage by initiating the skin-darkening process.
In the course of their study, 20 to 30 people were used in the experiment, darkening significantly with the effects lasting for several months, said Dr. Norman Levine, team member and dermatology professor at the UA.
At first, testing side effects led to some gastrointestinal problems, but this was prevented when the hormone was applied directly to the skin rather than taken orally.
Melanotan II was discovered by accident during testing. It differs slightly from Melano-tanin in biomechanical structure but retains the same melanin-producing qualities.
It also aids in the treatment of erectile dysfunction. Levine said that benefit cannot normally be tested in the United States, but the team received approval for a Physician Sponsored Investigated New Drug Application, which allowed limited evaluation of the hormone's effectiveness in this capacity.
The inventors have founded the Melanotan Corp. to license their invention to other companies. An Australian company, Clinuvel Pharmaceuticals Ltd., is currently testing Melanotan for commercial use. A New Jersey-based company, Palatin Technologies Inc., is testing Melanotan II and its enhanced qualities.