The call-up of reservists for the Persian Gulf buildup is striking medical care hard in rural America, leaving some small towns without doctors and forcing retired physicians back to work.

Dr. Victor Hoefner Jr., 70, was enjoying his retirement last month when his son, Dr. Victor C. Hoefner III, an Army National Guardsman, was called up for duty in the Persian Gulf.Now the elder Hoefner has taken over his son's family practice in this western Colorado community.

The Pentagon won't say how many doctors have been called up, citing security. In addition to the activation of members of the Army, Navy and Air Force reserves, the Army has begun forcing some retired medical officers back into uniform.

The effect of the call-up is quickly felt in small towns, and the indefinite duration of the crisis is adding to the problem, according to rural health experts.

"Are we talking three months, six months or a year?" asked Toby Turner, spokeswoman for the National Rural Health Association in Kansas City.

"Rural health has been in crisis anyway, and losing 50 percent of your small hospital's staff at one time is just too much of a blow. The military is just filling slots in these units without paying any attention to a medical reservist's role. The likelihood of a critical position being affected is greater and the likelihood of having adequate backup is less than a large hospital," said Al Chechik, spokesman for the Wisconsin Hospital Association.

The call-up of physicians, nurses and technicians has the potential to strip the U.S. Public Health Service staffs on Indian reservations, although not too many have been called as yet, officials said.

The Public Health Service hospital in Crownpoint, N.M., serving Navajos and members of other tribes in the area, lost its only ear, nose and throat specialist.

"The Public Health Service is part of the armed services, and we sign a statement that we can be pulled for non-combatant duty," said Dr. Annie Kusava, a pediatrician in Crownpoint, who carries the rank of lieutenant colonel.

In Verdigre, Neb., the lone physician was called up, leaving the northeast Nebraska community of 617 without a doctor.

Dr. Ken Pavlik, an Army Reservist, leaves a medical clinic and patients in the Knox County hospital and nursing home.

He arranged for Dr. D.J. Nagengast, who lives 25 miles away in Bloomfield, to make rounds and check on his patients.

"There is no question that this is going to be an inconvenience to a lot of people," Pavlik said.

While the number of physicians pulled out of rural areas apparently isn't great, their departure leaves a far larger gap than would that of their big-city counterparts.

"It hurts the rural hospitals where there have been shortages anyway," said Pete Moberg, spokesman for St. Mary's Hospital in Grand Junction. St. Mary's is a regional hospital, with accident victims or emergency surgery patients transferred from lesser-equipped rural hospitals.

"If a little hospital loses its doctor and a scrub nurse, there's going to be no surgery done there at all," Moberg said.

Dr. Jose Luis Rodriguez, the only plastic surgeon in Glenwood Springs, 90 miles east of Grand Junction, closed his office and referred patients to doctors in Grand Junction after he was activated.

In Wyoming, even more sparsely populated than Colorado, there are only about 600 doctors in the entire state and seven are already gone or on standby.